Kỹ năng phân loại và phương pháp giải chi tiết bài tập trắc nghiệm Vật lý 12 (Trọng tâm): Phần 1

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Phần 1 tài liệu Phân loại và phương pháp giải chi tiết bài tập trắc nghiệm Vật lý 12 do ThS. Trần Thanh Bình biên soạn trình bày các phương pháp giải chi tiết bài tập trắc nghiệm Vật lý về các chủ đề: Động lực học vật rắn, dao động cơ, sóng cơ. Mời các bạn cùng tham khảo nội dung chi tiết.

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Nội dung Text: Kỹ năng phân loại và phương pháp giải chi tiết bài tập trắc nghiệm Vật lý 12 (Trọng tâm): Phần 1

ThS. TRAN THANH BINH PHAN LOAI VA PHUOING PHAP GIAI CHI T I E T BAI TAP TRAC NGHI|M V A T L I 12 B I ^ N S O A N T H E O C H U O N G T R I N H M(5| D A N H C H O H Q C S I N H B A N N A N G C A O VA B A N C O B A N • T6m t i t If thuyet. • Phan logi theo tCfng van de. • C6c phudng phap gi^i bai t§p + b^i t§p. mlu cho tCrng v§'n de. • B^i t$p va If thuyet trie nghiem. • Bai tap luyen tap cuoi m6i chUdng. N H A Y I I A T R A M FiAi w n r o i i o c G I A T P HO CHf MINH
1 Ldf N O I D A U C^' h k m giijp cdc em hoc s i n h c6 t a i lieu t o t k h i hoc m o n V a t l i 12, chiing t o i bien soan quyen " P h a n loai va philcfng phap g i a i c h i t i e t b ^ i t a p trac n g h i e m V a t h' 12 t r o n g t a m " . T r o n g quyen sach n a y c6 10 chUofng. M o i chucfng deu c6 cau triic nhif sau: PHAN I: TOM TAT LI THUYET TRQNG TAM CUA CHUdNG. ( N h ^ m giup cac em hoc s i n h nMm vufng l i thuyet de c6 t h e l a m cdc cau h o i trSc n g h i e m l i thuyet cua chucfng). P H A N II: P H A N LOAI TL/NG V A N DE VA PHLTONG P H A P GIAI BAI T A P TLTNG VAN D E . ( M o i v a n de, m o i l o a i deu c6 cac b ^ i t a p mau, cac cau t r i e n g h i $ m b a i t a p ciia tiTng v a n de, t i f n g l o a i , b a i t a p luyen t a p cua chucfng). PHAN III: DAP AN CUA CAC CAU TRAC NGHIEM LI THUYET + BAI TAP TRAC NGHIEM VA BAI TAP LUYEN TAP. (Tat ca cac cau t r i e n g h i e m va b a i t a p deu c6 hudng d a n g i a i va dap dn). C h i c c h i n r i n g , neu cae em hoc s i n h chiu k h o l a m cac eau t r i e n g h i e m va hki t a p t r o n g quyen sach nay v i n i m t h a t vi^ng tCrng v a n de t r o n g quyen sach n a y m p t each day dii t h i c i c em se eo k e t qua t o t m o n V a t l i t r o n g c i e ki thi. Day eung la t a i lieu t h a m khao cho g i i o v i e n eung n h u phu h u y n h hoc sinh t r o n g viee giup c i e em hoc to't m o n V a t l i 12. Tuy t i c gia c6 r a t nhieu eo g i n g t r o n g qua t r i n h bien soan, n h u n g c h i c r i n g quyen s i c h k h o n g t h e t r a n h k h o i nhiJng t h i e u sot. M o n g q u i v i gido v i e n , cac bac phu h u y n h va cac em hpc s i n h c6 nhiirng y k i e n d6ng g6p de l i n t d i b a n quyen s i c h se h o a n ehinh han. Chan t h a n h c a m an. Tdc gia I / I
ChiTtfng I . DQNG LlTC HOC VAT RAN 1 P H A N I: T O M T A T L I T H U Y E T Van de 1: CHUYEN DQNG CUA VA T RAN QUA Y QUANH MQTTRUC CODINH 1. Tpa d6 g6c * K h i v a t r a n quay quanh m o t true eo' d i n h t h i : - M o i diem tren vat vach mot dUcfng t r o n n k m trong mat phang vuong goe v d i true quay, c6 ban k i n h bkng khoang caeh tiT diem do den true quay, eo tarn d t r e n true quay. - M o i d i e m t r e n v a t deu e6 eung m o t goe quay. * Tpa do goe (p = ( O x , O M ) De don g i a n t a c h i xet v a t quay theo m o t ehieu va thiJdng ehon chieu quay eiia v a t la chieu diTcfng -> k h i do (p > 0. 2. Tdc do g6c a) Toe do goc trung binh (conJ _ (p - cPo _ A(p t-t„ At Trong do: • (po: Toa do goe lue dan t a i thc(i d i e m to (rad). • (p: Toa dp goc liie sau cf t h d i d i e m t (rad). • to: T h d i d i e m lue dau k h i v a t eo cpo (s). • t i : T h d i d i e m liic sau k h i v a t c6 (p (s). • cotb: Toe dp goe t r u n g b i n h t r o n g t h d i gian At (rad/s). • Acp: G6c ma m o t v a t quay dupe t r o n g t h d i gian At (rad). • A t : T h d i gian quay goe Aep (s) b) Toe do goc tiic thai (co) Toe dp goc ttre thdi t a i thdi diem t la dai lupng dac tntog cho miJc dp quay cham hay quay nhanh cua v ^ t r ^ quanh mpt true eo' dinh t a i thdi diem do. Acp dcp m = lim =
3. Gia tdc g6c 5. van t6c Mh gia t6c cua c^c di^m tr§n v§t a) Gia toe goc trung binh CHUYEN DQNG CHUYEN DQNG Aco QUAY TRON DEU QUAY TRON BIEN DOI DEU K h i v a t r a n quay t r o n deu t h i K h i v a t r ^ n quay t r d n b i e n d 6 i At vectcf v a n toe m o t d i e m nao do deu t h i veeto v a n to'e ciia m o t Trong do: t r e n v a t c h i thay d o i ve hUcing d i e m nao d(3 t r e n v a t thay d o i ma k h o n g thay doi ve do IcJn. ea ve hudng va do IcJn. • Ytb: Gia toe goe t r u n g b i n h (rad/s^) K h i v a y r a n quay t r o n deu t h i K h i v a t r d n quay t r o n bien doi • Aco: Do bien t h i e n toe do goe (rad/s) gia toe toan p h a n cung ehinh l a deu t h i gia toe toan phan bao gia toe hucJng t a m a„ (gia toe gom gia toe tiep tuyen va gia toe • At: T h 6 i gian m a v a t b i e n t h i e n Aco (s) phap tuyen). phap tuyen (gia toe hirdrng tam). b) Gia toe goc tiic thai (y). a = a„ + a^ Gia toe goc tiJc t h d i t a i t h d i d i e m t l a d a i l u g n g dac t r i m g cho sir b i e n V 2 Bg Ian: + a: a =a =— = CO .r t h i e n eiia toe do goe c3r thcfi d i e m t k h i v a t xin quay quanh m o t true. r V(Ji: Aco dco • a„ vuong goe v , dac trUlig cho Y = lim = co'Ct) '^'^n At dt sU thay doi ve hucjrng cua v . V 2 a„ = — = CO .r 4. Che phadng trinh c!6ng hoc cua c h u y i n dSng quay CO phuong eiia v , dac trUng CHUYEN DpNG cho sU thay doi ve do 16n eiia v . CHUYEN DQNG QUAY QUAY IRON DEU TRON BIEN DOI DEU a, = r.Y • CO = h ^ n g so • 0) = o)o + Y-t • cp = cpo + cot • cp = cpo + COo.t + - i — • Y = 0 Cdc liCu y: • co^ - co^ = 2Y(CP - cp„) 0 i X * K h i v a t r ^ n quay t r o n deu t h i * N e u chon chieu ducfng cCing chieu CO k h o n g doi -> T , f k h o n g doi. quay cua v a t r ^ n t h i : • Y > 0 k h i v a t quay n h a n h d a n deu (co t a n g dan deu theo At) Van de 2: PHL/ONG TRINH DQNG Ll/C HQC CUA VA T RAN QUA Y • Y < 0 k h i v a t quay cham d a n QUANH MQT TRUC CO DINH deu (co g i a m dan deu theo At) 1. Momen lUc ddi v6i true quay • T o n g quat: Momen lue M cua life F d o i v d i v a t r a n co true quay co d i n h l a d a i lucfng dac t r u n g cho tdc dung c o d i n h l a d a i lifcfng dae trUng cho tae dung l a m • co.Y > 0 -> vat quay nhanh dan deu. quay v a t r ^ n quanh true co d i n h do va dUOe do bang t i c h so ciia lUc va • oj.Y < 0 ^ vat quay cham dan deu. each tay don. M = F.d = F.r.sina
Trong do: c) V a t l a h h i h t r u r o n g hoac v ^ n h t r o n quay quanh true d i qua tarn. • M : M o m e n cua life ( N . m ) . , (A) • F: Luc tAc dung (N). I • d: C a n h tay don (m). (Khoang each tCr true quay den gid cua life) I = m.R= 2. Momen quSn tinh (I) - Momen quan t i n h I d o i v6i m o t true la d a i lu'Ong dac t r u t i g eho miJe quan t i n h cua v a t rMn t r o n g chuyen dong quay quanh true ay. d) V a t Ik h i n h t r u dSc hay dia t r o n mong quay quanh true d i qua tarn. 1= 1 m, .r (A) (A) - Momen qudn t i n h c6 dp I d n phu thupe vao k h o i iMng v a t r ^ n , phu thupc vao sir p h a n bo' k h o i li^png eiia v a t r ^ n d o i vcJi true quay (gan h a y xa c I = -mR'^ true quay). 2 3. PhUdng trinh dong luc hoc cua vSt r3n quay quanh m6t true cd dinh M = I.y Trong do: e) V a t l a h i n h cau d i e quay quanh m p t true d i qua t a m . • M : M o m e n lire (N.m) • I : M o m e n qudn t i n h (kgm^) • y: Gia toe goe (rad/s^) I = -mR^ Nhqn xet: Ydi cung m o t M o m e n t h i 5 • Neu I i d n y nho - > k h o t h a y doi toe dp goe. • Neu I nho -> y i d n -> de t h a y doi to'e dp goe. 4. Momen quSn tinh cilia m$t s6 v$t dfing ch^t Van de 3: MOMEN DQNG LI/0NG DINH LUAT BAO TO AN MOMEN a) V a t l a t h a n h m a n h dong chat, k h o i lupng m , chieu d a i I eo true quay l a DQNG LU0NG dudng t r u n g true cua t h a n h . 1. Momen dOng ladng. Momen dong liTpng eiia v a t r ^ n d o i v d i m p t true quay b^ng t i c h so eua (A) momen quan t i n h cua v a t doi v d i true quay do va toe dp goe cua v a t quay I = —ml' 12 quanh true do. J L = I.a) (u)>0-»L>0;a)
Dieu kien dp dung dinh ludt: TRAC NGHrEM LI THUYET K h i t o n g d a i so cua cac momen ngoai lye dat l e n mot v a t r ^ n (hay h$ v a t ) doi v d i mpt true quay b^ng k h o n g (hay cac momen ngoai lire t r i $ t tieu) C a u 1. M p t d i e m t r e n v a n h dia t r o n each true quay d i qua t a m m p t k h o a n g R Luu y: K h i I doi v d i true quay k h o n g doi -> to = 0 hoac w - h k n g so. k h i dia quay t r 6 n deu quanh true t h i toe dp d ^ i va toe dp goc eiia d i e m do c6 (Vat k h o n g quay hoae v a t quay deu) quan he v d i nhau theo bieu thiJe nao t r o n g cac bieu thiifc sau? Van de 4: DQNG NANG CUA VAT RAN QUA Y QUANH A v - - . B. v = - . C. 0 3 = - . D . R = vlco. R CO R MQTTRUC CODfNH C a u 2. H a i hpc s i n h A va B diing t r e n mpt ehiec du quay t r o n deu quanh true 1. D6ng nSng cCia m6t vat rjn quay quanh m6t true c6 dinh C O d i n h d i qua t a m . Hoe s i n h A d ngoai r i a , hoc s i n h B d each t a m m p t doan b^ng mpt p h a n t u b a n k i n h chiee du quay. Gpi T A , TR la ehu k y quay cua hoc sinh A va hoe s i n h B . Lue nay t a cd: Trong do: • W,i: D o n g n ^ n g eua v a t r a n quay quanh m p t true (J) A. T A = T B - ' ^ B . TA < TB- C. T A > T R . D . T A = 4T„. • I : M o m e n quan t i n h cua vat (kgm^) C a u 3. Klpt dia CD coi n h u chuyen dpng t r d n deu xung quanh true d i qua t a m • co: Toe dp gdc cua v a t (rad/s) eiia dia. Gpi E va F I a n lupt la d i e m d ngoai r i a va d i e m d each t a m dia m p t 2. Dinh li dong nSng doan b^ng nuTa ban k i n h cua dia. Gpi VR, V F , fs, fp I a n lupt la toe dp d a i va A = W, - Wd,,,-,„ t ^ n so ciia cac d i e m E va F. K e t l u a n nao sau day la diing? A. VE = Vp; fe = B. VE = Vp; = 2iv. Trong do: • A: Cong eiia ngoai lue (J) C. vp = 2VE; ffi = fp- D- VE = 2VF; h = fp- • ,^ : Dong nftng lue dau (J) C a u 4. M p t dia quay t r o n deu quanh true doi xii'ng d i qua t a m . Gpi A la d i e m d • Wj : Dong nftng lue sau (J) ngoai r i a , B l a d i e m each true quay m p t doan b a n g mpt p h a n ba ban k i n h dia. Gpi (DA, COB, YA, YB I a n lupt l a toe dp gdc va gia toe gdc cua ede d i e m A va Luu y: Neu v a t chi c6 chuyen dpng quay quanh true t h i : W j = B . Chpn cau k e t l u a n diing. • Neu v a t thuc h i e n dong thcfi h a i ehuyen dpng la quay quanh A. COA = 2(0B; YA = YB- B. (OA = cou; YA = 2YB. true va t: tinh tien thi: W j = + C. tOA = COB; YA = YB- D - " A = COR; YA = YB- 3. Djnh li v l true song song C a u 5. M p t dia CD quay t r d n deu quanh true d i qua t a m dia. M p t d i e m bat k y n k m d mep dia se: 1(A) = 1(0) + inx^ A. k h o n g cd gia toe t i e p t u y e n I a n gia toe phap tuyen. Trong do: B . cd gia tdc phap t u y e n n h u l i g k h o n g cd gia toe t i e p tuyen. • 1(A): M o m e n quan t i n h eiia m p t vat doi v d i true quay ( A ) (kgm^) C. C O gia tdc t i e p tuyen va ed ea gia toe phap tuyen. • IQ: Momen quan t i n h eiia true di qua trong tarn G song song vdi (A) (kgm^) D. ed ea gia tdc t i e p t u y e n va gia to'e phap tuyen n h u i i g gia toe phap t u y e n • m: K h o i lupng v a t rSn (kg) Idn hon gia toe t i e p t u y e n . • x: K h o a n g each vuong gdc giSa true ( A ) va true song song qua (G) (m) C a u 6. M p t v a t rSn quay t r o n deu quanh true eo' d i n h d i qua v a t t h i m p t d i e m Hinh minh hga dinh li: t r e n v a t d each true quay m p t doan r 0 se cd (A) (G) ' A. toe dp gdc thay doi. B . ehu k y quay t h a y doi. 0) C. tdc dp dai t h a y doi. D. vecto van tdc dai t h a y doi n h u n g to'e dp Aki eiia d i e m dd, k h o n g ddi. G C a u 7. M p t vat r ^ n quay t r o n deu quanh mpt true cd d i n h . Gpi N la so dao dpng ma vat thue h i e n t r o n g t h d i gian At, cpo va cp la tpa dp gdc lue dau va lue sau, co la tdc dp gdc cua vat r a n . Chpn bieu thiire sai t r o n g cac bieu thde sau: A. T : . — . B T = — . C. N = ^ ^ ^ . D. (p = (po - «At. CO N 27;
C a u 16. M p t v a t rMn quay bien d o i deu quanh m p t true co d i n h d i qua v a t rin. C a u 8. Bieu thiJc nao sau day l a dung k h i n 6 i ve dp I d n cua gia toc ph^P t u y e n Chon phat bieu sai t r o n g cac p h d t bieu sau: (gia toc hudng tarn)? A. Gia toc goc l a h k n g so. V v^ B. Toe dp goc l a m p t h a m bac n h a t d o i v d i t h d i gian. A. an = - . B. an = w.R. C. an = — . D. a^ = (w.R)^. C. Toe dp gdc 1^ m p t h k n g so. C a u 9. Bieu thiJc nao sau day l a dung k h i n o i ve do I d n ciia gia toc t i e p t u y e n D. T r o n g chuyen dpng quay b i e n d o i deu ciia v a t r k n quanh m p t true co' d i n h cua v a t rSn quay b i e n d o i deu quanh mot true co dinh? di qua no t h i toe dp goc tSng hay g i a m nhiJng luang eo dp I d n b k n g nhau t r o n g nhiJng k h o a n g t h d i gian b k n g nhau. A. at = r.y. B. a t = - . C.at=-. D. at = — . Y r r C a u 17. M p t v a t r k n quay v d i toc dp goc k h o n g d o i quanh m p t true ed d i n h d i C a u 10. M o t v a t r ^ n quay b i e n d o i deu quanh m o t true d i qua v a t r ^ n . Chon qua vat. So' vong quay m a v a t quay dUde t r o n g t h d i gian t ke til luc v a t b a t goc t h d i gian to = 0 la luc v a t bat dau quay. Goi t i , t 2 l a cac t h d i d i e m liic sau dau quay se: (t2 = 2 t , ) . N e u xet m o t d i e m t r e n v a t r ^ n each true quay T ^0 t h i : A. t i le v d i t l B. t i le v d i t . C. t i le v d i D. t i le v d i - . . t A. a,, = 2a,^. B. a,^ = 2 a , . C. a,_ = ^ . D. a, = a,^. C a u 18. M p t v a t r k n quay v d i gia toe goc k h o n g d o i quanh m p t true ed' d i n h d i C a u 11. Bieu thiJc nao t r o n g eac bieu thiic sau k h o n g the ap dung cho v a t r ^ n qua vat. Goc ma v a t quay dupe sau t h d i gian t , ke tCr luc b k t dSu quay se quay bien d o i deu quanh m p t true co d i n h d i qua vat? A. t i le v d i t^. B. t i le v d i t . C. t i le v d i \ D. t i le v d i - . t t A. 9 - cpo = o)o-t + • B. (0^ - (OQ = 2Y((P - cpo)- C a u 19. M p t v a t r ^ n quay n h a n h d a n deu quanh m p t true eo' d i n h xuyen qua vat. M p t d i e m t r e n v a t r S n k h o n g n k m t r e n true quay va each true quay m p t C. cp = (po + cD.t. D. © = 0)0 + y.t. doan r ^ 0. Chpn p h a t bieu dung t r o n g eac p h a t bieu sau: C a u 12. Bieu thiJe nao t r o n g eae bieu thiJe dudi day l a sai k h i t i n h gia toe t o a n A. Td'c dp gdc k h o n g phu thupc r. p h a n ciia v a t r ^ n quay b i e n d6'i deu quanh m o t true eo d i n h d i qua vat? B. Gia to'c gdc phu thupc r. A.a= J ^ ^ . B. al=a'-al C. Gia toe t i e p tuyen k h o n g phu thupc r. D. Gia toe phap t u y e n k h o n g phu thupc r. C.rV = a^-f—1. D. a'= ^co^r + ry . C a u 20. M p t v a t r k n quay quanh m p t true co' d i n h xuyen qua v a t . Cac d i e m I r j t r e n v a t r k n k h o n g thupc true quay se C a u 13. P h d t bieu nao sau day 1^ d u n g d o i v d i v a t r ^ n eo chuyen dpng quay A. vaeh n e n cac dudng t r o n n k m t r o n g m a t p h k n g vuong gdc v d i true quay. deu quanh m o t true? B. ed eung v a n toe d a i d eung m p t t h d i diem. A. Toc do goc l a m o t hSng so. C. quay dUde nhi^ng gdc k h o n g b k n g nhau t r o n g eung m p t k h o a n g t h d i gian. B. Toe dp goc l a m o t h a m bae n h a t doi v d i t h d i gian. D. ed gia to'c gdc va to'c dp gde la h k n g so. C. PhUdng t r i n h chuyen dpng l a m o t h a m bac h a i doi v d i t h d i gian. C a u 21. H a i dia t r o n dang quay D. Gia toe goc 1^ m o t hkng so. dong true va eiing chieu v d i C a u 14. Chpn phat bieu sai k h i n o i ve momen quan t i n h eiia v a t r ^ n toe dp gde coi, 0)2. M o m e n quan A. Momen quan t i n h phu thupc vao h i n h dang va k i c h thude ciia v a t . t i n h cua h a i dIa 1^ I i , I 2 . M a B. Momen quan t i n h phu thupe vao k h o i liTpng ciia v a t r ^ n . sdt d true quay k h o n g dang C. Momen quan t i n h k h o n g phu thupc vao v i t r i true quay ciia v a t r ^ n . ke. Sau do cho h a i d i a d i n h D. Momen quan t i n h k h o n g phu thupc v^o toc dp goc ciia v a t . vao nhau va quay v d i to'c dp C a u 15. M o t chiee du quay ehiu tac dung eiia m o t momen lue k h o n g doi. Chon gdc 0). Bieu thde t h e h i e n m d i v./a)2 phat bieu sai t r o n g eac p h a t bieu sau: quan he giOfa ede d a i li/dng coi, A. Gia toc goc ciia chiec du quay l a m o t h^ng s6'. ^ 2 , I i , I 2 , 0) l a : B. K h d i lUdng cua chiec du quay l a m o t h k n g so. A. I i ( O i = l2(02 + d i + 12)0). B. IiCO] + l2(02 = d l + l2)W- C. Toe dp cua chiec du quay 1^ m o t h^ng so. C. Iicoa + l2(0i - d i + l2)(i). D. Iicoi - I2CO2 = d l + h)o^- D. M o m e n qudn t i n h l a m o t h k n g so.
C a u 22. H a i dia t r 6 n m 6 n g n ^ m C a u 28. H a i d i a t r 6 n c6 c u n g m o m e n q u d n t i n h n g a n g c6 c u n g t r u e q u a y t h S n g d o i c u n g m o t t r u e q u a y d i q u a cac t a m d i a . L u c diJng d i q u a t a r n cua h a i d i a . d l u d i a m o t d i J n g y e n , d i a 2 q u a y v d i toe dp goe M o m e n q u a n t i n h ciia 2 d i a l a I j , u)2. B 6 qua m a s a t d t r u e quay. Sau do h a i d i a I2. L u c d a u d i a 1 d i J n g y e n , d i a 2 d i n h v a o n h a u v a q u a y c u n g toe d p goe (o. C h p n q u a y v d i to'c do CO2. B o q u a m a k e t l u a n d u n g k h i n d i ve d p n g n a n g cua h e h a i s a t do'i v d i t r u e q u a y . T h a n h e d i a lue sau so v d i lue d a u . V_/co d i a 1 xuo'ng d i a 2 sau m o t t h d i A. G i a m d i 2 I a n B. T a n g len 2 Ian. g i a n n g S n t h i ca h a i d i a q u a y v d i C. T a n g l e n 4 I a n D. G i a m di 4 Ian. Cling mot toe dp goe la: C a u 29. H a i r o n g rpe 1 v a 2 cd k h d i l i i p n g l a m , v a m 2 = 2 m i , b a n k i n h cua A . 0) = B . (0 = C. w = D . 0) = r d n g r p e 1 ga'p 4 I a n b a n k i n h c i i a r d n g r p e 2. T i so giCa j - Ik: h C a u 23. M o t n g i r & i d i J n g t r e n m o t c h i e e b a n x o a y d a n g q u a y . L u c d a u n g u d i a y A . 2. B . 4. C. 6. D . 8. d a n g t a y r a t h i g h e v a n g u d i q u a y v d i t o e d p goe l a coi. B o q u a m a s a t d t r u e C a u 30. H a i d i a t r b n m o n g c6 cung d p n g n a n g quay, t i so giOfa m o m e n q u a n t i n h eiia q u a y . S a u do ngurdi a y t h u t a y l a i s a t n g i r d i t h i g h e v a n g i r d i q u a y v d i t o e d p goe C02. B i e u thiirc n a o d i i n g t r o n g eac b i e u thuTc sau? dia 1 v a d i a 2 d i qua t a r n cua d i a 1 v a d i a 2 l a i - = 4. H m t i so' toe dp goe —. A . Iicui - I2CO2. B . I1CO2 = l2Wi- C. IiCOi + 12(1)2 = 0 . D . coi > (02- A . 1. B . 2. C. 3. D . 4. C a u 24. M o t v a n d o n g v i e n t r U p t b a n g q u a y q u a n h m o t t r u e t h ^ n g d i J n g v d i h a i C a u 31. M o t t h a n h m a n h d o n g c h a t d i e n d i e n d e u , c h i e u d a i t h a n h l a I, k h o i t a y d a n g r a v a c6 toe dp goe coi, m o m e n q u a n t i n h I i . S a u do v a n d o n g v i e n l i i p n g t h a n h l a m . T h a n h ed t h e q u a y x u n g q u a n h m o t t r u e n ^ m n g a n g d i q u a t h u t a y l a i d o t n g p t t r o n g k h o a n g t h d i g i a n n h o de ed t h e bo q u a a n h h u d n g m o t d a u eiia t h a n h v a v u o n g goe v d i t h a n h . B d q u a m p i m a s a t v a sdc c a n . eiia m a s a t do'i v d i m a t b a n g . L u c n a y v a n d p n g v i e n q u a y v d i t o e dp goe l a C02, m o m e n q u a n t i n h l a I2. C h p n k e t l u a n d u n g . B i e t m o m e n q u a n t i n h cua t h a n h l a I = v a g i a toe r o i ta. do l a g. H o i A . M l = (02; I i = I2. B . coi = (02; I i < h- o C. COi > M2; I I > D . (Oi < (02; I i > 12- n e u t h a n h diTpe t h a k h o n g v a n to'c d a u t i f v i t r i nhm n g a n g t h i to'c dp gdc cua C a u 25. M o t v a n d p n g v i e n triTpt b a n g q u a y q u a n h m o t t r u e t h ^ n g d i J n g v d i t o e t h a n h k h i q u a v i t r i t h i n g d d n g l a bao n h i e u ? dp goe (iJi, m o m e n q u a n t i n h I i k h i h a i t a y t h u l a i s a t n g u d i . S a u do v a n d p n g 3g 2g 3g A . (0 = B . (0 = C. (0 = D . CO = 21 ^31 ' ^ I 121 • v i e n d a n g t a y r a t h i t h a y t o e d p goe lue n a y l a 0)2 = — . B o q u a m a s a t giiJa C a u 32. M o t t h a n h A B d o n g chat ed chieu d a i I cd t h e quay t r o n g m a t p h a n g t h a n g n g u d i v d i m a t b a n g . G p i I i , I 2 , vf^^ , W j _ I a n l u p t l a m o m e n q u a n t i n h v a d p n g d i i n g qua m o t true n k m n g a n g d i qua m o t dau cua t h a n h v a v u o n g gdc vdi t h a n h . n a n g cua v a n d p n g v i e n k h i h a i t a y t h u l a i sat n g u d i va k h i h a i t a y d a n g r a . T h a n h ed t i e t d i e n deu, k h d i liTpiig m , gia toe rcri t i l do l a g, I = ^ . B o qua m p i m a Chpn ket luan diing. o 1 sat va sure can. T h a n h d a n g d d n g y e n d v i t r i can b k n g . H o i can p h a i t r u y e n cho A . I2 = 2I1; w, B . I , = 2I2; w. = 2w, t h a n h m o t toe dp gdc l a bao n h i e u de t h a n h quay d e n v i t r i n k m n g a n g . C. I2 = 2 1 , ; w d, . -= - 2" wd ., • D . I2 = 2I1; vv,^ = w
P H A N II: B A I T A P T R A C NGHIEM C2.Tac6thld6itCr4^ sang ^ . phut s + BAI TAP LUYEN TAP Cu t h e n h u sau: 1 2 0 0 vong/phut = 1 2 0 0 . ^ ^ ^ ^ = 4 0 rad/s Van de 1: VAT RAN QUA Y TRON DEU 60s (0 = 4071 (rad/s) PHlJolNG P H A P Trong do b) G6c ma v a t quay diTcfc t r o n g t h d i gian 4 s 1^: tp — (PQ = co.t • T: Chu k i quay ciia v a t (s). I. C h u y e n dpng tron deu. cp - cpo = 4071.4 cp - cp,| = 1 6 0 7 c ( r a d ) • f: T a n so (Hz) (v6ng/s). N (0 • t : T h 6 i gian quay N v o n g (s). B a i 2. Roto eiia mot dong ecf quay t r o n deu quanh m o t true co d i n h . B i e t r k n g • N : So' vong. eiJ m 6 i p h u t t h i Roto quay d M c 1 2 0 0 vong. T i m : a) Chu k y quay ciia Roto. T • V: Toe do d a i ( v a n toe d a i ) (m/s). b) Gc3c ma ROto quay d M c t r o n g 2 s. • V = (o.r • co: Toe do goe (van toe goc) (rad/s). c) So vong ma Roto quay diiac t r o n g 2 s. ; • an = oj .r = — • r : B a n k i n h quy dao cua v a t (m). r HUdng ddn gidi • Sin. Gia toe phap t u y e n (gia toe Tom tat • a t = 0 (chuyen dong deu) Moi phut t h i Roto quay duoe 1 2 0 0 vong a) Chu k y quay cua Roto hirdng tarn) (m/s^). • (p = (po + co.t => 1 2 0 0 vong/phut 271 271 • a t : Gia toe t i e p t u y e n (m/s^). T = • a = a„ 1200.27Trad 4071 • 0) = 271.f • a: Gia toe t o a n p h a n (m/s^). M = T = 0,05(s) 60s I I . luvtu y • cpo: Toa do goe liic dau (rad). = 4071 r a d / s b) Goe m ^ Roto quay ducfc t r o n g 2 s. K h i v a t r ^ n quay t r o n deu t h i : • 9: Toa do goe luc sau (rad). a) T = ? cp - cpo = co.t • co: K h o n g doi (la h ^ n g so). b) cp - cpo = ? => cp - cpo = 4 O 7 1 . 2 • oj > 0: Neu vat quay theo chieu e) N = ? cp - cpg = 807i(rad) diJOng. c) So vong ma Roto quay diJgrc trong 2 s. • 0) < 0: Neu v a t quay ngi/crc chieu ^ 9-9o ^ SOn ducfng. 22 N = 4 0 (vong) BAI T A P M A U B a i 1. Mot banh xe quay deu quanh mot true eo d i n h vdi t a n so 1 2 0 0 v5ng/phut. B a i 3. M o t b a n h xe quay t r o n deu quanh m o t true co d i n h . B i e t toa do gc5c a) T i m toe dp goe cua b a n h xe. iue dau la - r a d va toa do g6c sau t h d i gian la i s la ^ rad, ban k i n h b) Goc ma b d n h xe quay duoc t r o n g t h d i gian 4 s. 3 0 0 b a n h xe la 50 em. T i m Hudng ddn gidi a) Toe do goe cua b a n h xe. Nhdn xet: Do b a n h xe quay deu quanh m o t true co d i n h n e n t a can silr d u n g b) Toe do d a i eua m o t d i e m t r e n v a n h b d n h xe. eac k i e n thiJe cua chuyen dpng t r o n deu. e) Gia toe huc?ng t a m cua m o t d i e m t r e n v a n h b a n h xe. Tom tat a) De cho t a n so 1 2 0 0 v6ng/phut B&nh xe quay deu 1 2 0 0 vbng/phut Cl:=> f = 1200 ^ = 2 0 ^ = 2 0 Hz Tom tat Hiidng dan gidi a) CO = ? 60s s ai) Toe do g6c ciia b a n h xe b) cp - (po = ? (0 = 2nf ^ CO = 271.20 • cpo = — rad Ap dung cong thiic: 3 CO = 407t (rad/s) (p - cpo = co.t
_ IL _ 1 C a u 2. K i m p h i i t c i i a 1 chie'e d o n g h 6 g a p 4/3 I a n c h i e u d a i k i m g i d . C o i cac • (p = — rad 3 3 ~ 3 k i m n h u q u a y d e u . T i so g i a t o e h i f d n g t a m giura d a u k i m p h u t v a d a u k i m (0 = 7 t ( r a d / s ) gid la . t = - s b ) T o e do d a i c u a m o t d i e m t r e n v a n h b a n h xe. A. 92. B . 108. C. 1 9 2 . D . 200. • R = 50 c m = 0,5 m V = M . R = 71.0,5 = 0,571 Cau 3. Mot banh xe quay deu quanh mot t r u e co dinh v d i t a n so 2400 a) (0 = ? V = l,57(m/s) v d n g / p h i i t . T o e do goc c i i a b a n h x e n a y l a b) V = ? A . 12071 (rad/s). B. 160;: (rad/s). c) an = ? C. 8071 ( r a d / s ) . D . 2407i ( r a d / s ) . c) G i a t o e h u d n g t a m c i i a m o t d i e m t r e n vanh Cau 4. R o t o cua mot dong co q u a y d e u , cii: m o i p h i i t q u a y d u o c 3 6 0 0 vdng. b a n h xe T r o n g 20 s t h i r o t o q u a y diroc m o t goc l a 1,57'^ A. 120071 rad. B. 24007t rad. R _0A_ C . 360071 r a d . D . 4 8 007r r a d . a„ « 4 , 9 3 ( m / s ^ ) C a u 5. M o t v a t - c h u y e n d o n g t r d n d e u v d i t o a do goc l u e d a u l a — r a d v a t o a do 2 27T B a i 4 . K i n i p h u t c u a m o t e h i e c d 6 n g h o c6 c h i e u d a i b a n g 2 I a n c h i e u d a i k i m goc luc sau l a r a d t r o n g t h d i g i a n 2 s. B i e t b a n k i n h q u y d a o t r d n c i i a gicf. Cac k i m coi n h u ' q u a y d e u q u a n h m o t t r u e co d i n h . T i m t i so giuTa to'c o do d a i cua d a u k i m p h u t v a d a u k i m g i d . v a t l a 10 c m . T o e do d a i c i i a v a t l a Hiidng dan gidi A . 7t/120 m / s . B . 7t/60 m / s . C. 7i/240 m / s . D . 7i/360 m/s Tom tdt Nhan xet: N e u x e m k i m gid va k i m p h u t quay t r d n C a u 6. M o t v a t c h u y e n d o n g t r d n d e u q u a n h m o t t r u e v a t q u a y 10 v d n g h e t 20 •Tphat= 60 p h u t = 1 g i d . d e u q u a n h m o t t r u e co' d i n h t h i : s. B a n k i n h q u y d a o c u a v a t l a 20 c m . G i a t o e h u d n g t a m cua v a t l a . T g i , = 12 gior. * T h d i g i a n de k i m g i d q u a y m o t v o n g l a 12 g i d A . 1,25 m / s ^ B . 0,65 m / s l C. 0,85 xnJ&\. 1,97 m / s l • Rphui = 2 Rgij,. ^ T„i, ^ 12 g i d C a u 7. M o t v a t q u a y t r d n d e u d e u co p h u o n g t r i n h : cp = 7[/2 + 27tt ( r a d ; s). Toa pillit _ • T h d i g i a n de k i m p h u t q u a y m o t v d n g l a 6 0 dp goc l i i c d a u v a c h u k i q u a y c i i a v a t l a ^gid phut = 1 gid ^ Tphut = 1 gid. A . 7i/2 r a d ; 2 s. B . 71/6 r a d ; 1 s. C. 71/6 r a d ; 1/2$. D . 7t/2rad; I s . * K h i x e t d i e m d d a u m i i t c i i a k i m g i d v a k i m p h u t t h i k h o a n g e a c h tCf t r u e C a u 8. M o t v a t q u a y t r d n d e u c6 p h u o n g t r i n h t o a d o : cp - n/4 + 6nt ( r a d ; s). q u a y d e n cac d i e m n a y b K n g d u n g c h i e u d a i cua k i m g i d v a k i m p h u t n e n Goc q u a y c i i a v a t s a u 2 s k e t i f l i i c t = 0 l a A. 871 r a d . B. IOTI rad. C. 127c rad. D. 147T rad. • T i m t i so t o e do d a i cua d a u k i m p h u t v a d a u k i m g i d fv = C3.R Van de 2: VAT RAN QUA Y BIEN DO I DEU T a co: ^ 271 =5" v = — .R (*) PHl/CfNG P H A P Trong do A p d u n g (*) cho d i e m d d a u k i m p h u t v a d a u k i m g i d I. P h a n loai * CO,): V a n to'c goc liic b a n d a u (rad/s) 271 R phiit 1. Quay nhanh dan deu ' pllllt = 24 2n 271 0 10 20 60 80 ... * (o: to'c do goc l i i c sau ( r a d / s ) . .R gid t 0 2 4 6 8 ... * y: to'c do goc (rad/s^). BAI TAPTRAC NGHIEM * cpo: T o a do goc l i i c d a u ( r a d ) . 2. Quay chdm dan deu Cau 1 . K i m p h i i t c i i a m o t c h i e c d o n g h o co c h i e u d a i b f t n g 4/3 c h i e u d a i eiia w ... 8 0 60 20 0 * (p: T o a do goc l i i c sau ( r a d ) . 40 k i m g i d . Cac k i m c o i n h u q u a y d e u . T i so toe do d a i c i i a d a u k i m p h u t v a d a u * a„: G i a tdc h u d n g t a m (gia to'c k i m gid la t ... 0 1 2 3 4 p h a p t u y e n ) (m/s^). A . 1/16. B . 16. C. 3/4. D . 4/3.
I I . C a c c o n g thtfc. * a t : G i a t o e t i e p t u y e n (m/s^). B a i 2. R o t o eua m p t d p n g ccf d a n g q u a y q u a n h m O t t r u e c6' d i n h v6i t6c d p g6c * a: G i n toe t o a n p h a n (m/s^). la 12071 r a d / s t h i b i h a m l a i v a q u a y c h a m din d e u s a u t h d i g i a n 10 s t h i CO = coo + Y-t toe dp g(5c c o n 407t r a d / s . CO - ml = 2y(cp - cpo) * r : B u n k i n h q u y c!ao e i i a d i e m a) T i m g i a toe goc c u a R o t o . xet ( h a y v a t dutfc x e t ) ( m ) . b ) T i m gdc q u a y v a so v d n g mk R o t o q u a y dMc t r o n g t h d i g i a n 10 s k e tiT (p = cpo + coo-t + 2 liic h a m . c) So v 6 n g m a R o t o q u a y dugrc k e tiir l u c b i h a m c h o d e n k h i dCfng h i n 1^ cp - ipo = (Oo-t + bao n h i e u ? + a. HUdng ddn gidi Tom tat a„ = CO . r • coo = 1207T ( r a d / s ) C h o n e h i e u q u a y cua R o t o l a m c h i e u duc(ng, goc at = r . y • CO = 407r ( r a d / s ) t h d i g i a n (t = 0) l a luc Roto b ^ t d a u b i h a m l a i . t = 10 s a) G i a t o e goe eua R o t o * Li/u y: C a c h n h a n b i e t v a t q u a y n h a n h d a n d e u h a ^ c h a m d a n d e u : a) y = ? - CO - cOo 4071 -- 12071 • N h a n h d a n deu Y = - b ) cp - (po = ? 10 * (Oo = 0 N = ? t r o n g 10 s —»• y = -87i(rad/s^) * (o.y > 0 ke tir luc h a m . b) Goc quay eiia R o t o quay diTOc s a u 10 s k e tCr l u c • C h a m d a n deu c) N = ? k e t d l i i c b ^ t d a u bi h a m l a i . ham cho d e n l u c * (o.y < 0 yt^ ddng h^n. cp - cpo = COo.t + • Chuyen dong quay b i e n doi deu t h i y k h o n g doi (-87t).10' cp - cpo = 1207r.lO + BAI T A P M A U (p-cpo = 80071 ( r a d ) Bai 1. M o t b a n h xe q u a y n h a n h d a n d e u q u a n h m p t t r u e tiT t r a n g t h a i durng < So' v o n g rak Roto quay dircfe i l n g v d i g6c quay t r e n . yen v a sau 5 s t h i d a t d u g c t o e do goc l a 10 r a d / s . T i m : N= « N = ^ « | N = 400vong a) G i a toe goc c i i a b a n h x e . 271 271 b ) Goc q u a y cua b a n h x e t r o n g t h d i g i a n 5 s k e t i r t r a n g t h d i d i l n g y e n . e) So v d n g m a R o t o q u a y diToc k e tijf l u c h a m p h a n h cho d e n l u e di^ng h ^ n . c) So v o n g m a b a n h x e q u a y dugfe t r o n g t h d i g i a n 5 s d t r e n . N = (1) 2K Tom tat Hiidng dan gidi • T i m cp - cpo = ? • tOo = 0 C h p n c h i e u q u a y c u a b d n h x e l ^ m c h i e u ducfng, goe D o l u c sau R o t o dCtog l a i - > co = 0 • t = 5 s t h d i g i a n (t = 0) l a liic v a t b ^ t d a u quay, co^ - cof, = 2y (cp - cpo) • CO = 10 raci/s a) G i a toe goc e i i a b a n h xe. 2 2 CO -COn 0 ' - (12071)=' _ -1440071^ a) y = ? (o-coo 10-0 Y = y = 2(rad/s') 2y 2.(-87r) -16;: b) cp - (po = ? cp - cpo = 90071 ( r a d ) (2) c) N = 90071 The ( 2 ) v a o ( l ) ^ N = o |N ^ 4 5 0 ( v d n g ) b) G6c m a b d n h x e quay difcfc t r o n g t h d i g i a n 5 s k e tiT t r a n g t h d i diJng y e n . 271 y.t^ 2.5' cp - CPo = (Ofl.t + = 0.5 + B a i 3. M p t d I a m a i c6 b a n k i n h 4 0 c m hAi d a u q u a y k h o n g to'c dp goc l u c d a u cp - (p„ = 2 5 ( r a d ) v d i g i a t o e goc k h o n g d o i c6 d p I d n l a 27i (rad/s^). T i m : c) So v o n g m a b a n h x e q u a y dugc t r o n g t h d i g i a n 5 s d t r e n . a) T o e d p goe m a d i a m a i d a t dugtc sau 4 s k e iii l u c t = 0. 25 b ) G i a to'c t i e p t u y e n , g i a toe p h d p t u y e n c u a m p t d i e m t r e n v d n h d i a t a i N = N = 3,98 ( v o n g ) 271 _ t h d i d i e m t = 4 s k e t d l i i c t = 0. 2.3,14
c) Gia toe toan ph^n ciia mot diem tren vanh dia tai thdi diem 5 s ke tCf C a u 10. T a i th6i diem t = 0, mpt bdnh xe dap bdt dau quay quanli IUUL true vdi luc t = 0. gia toe goc khong doi. Sau 4s no quay dupe mpt goc 20 rad. Toe dp goc va gia toe goc ciia banh xe tai thcfi diem t = 5 s la Tom tat Hu6ng ddn gidi A. 12,5 rad/s; 2.5 rad/s'. B. 20 rad/s; 2,5 rad/s^ • R = 40 em Chon ehieu quay ciia dia mai lam chieu dUcfng va C.IO rad/s; 22 rad/s^ A. 10 rad/s; 12 rad/s"". • (Oo - 0 goe thdi gian (t = 0) la luc dia mai bdt dau quay, C a u 11. Mpt banh xe eo ban kinh I m quay nhanh dan deu trong 4 s to'c dp goc • y = 271 rad/s^ a) To'c do goe cua dia mai dat duoe sau 4 s. tang tCf 20 rad/s len 30 rad/s. Gia to'c goe eiia banh xe v^ gia to'c hir(Jng tarn a) (0 = ? sau (I) = 0^0 + Y-t ciia 1 diem tren vanh banh xe sau 2s la t = 4s o (0 = 0 + 271.4 A. 2 rad/ s'^; 400 mJs\. 2,5 rad/ s^; 625 m / s l b) at = ? an = ? tai w = 87t (rad/s) C. 4 rad/s^ 300 m / s l D. 5 rad/ s^; 196 m/s^ t = 4s C a u 12. Mpt banh xe C
C a u 19. 1 l o n g cac p l i u o i i g t i i n h sau, phuong t r i n h n^o m6 t d quy l u d t quay 4. V a t la h i n h t r u d&c hay dia t r o n m o n g quay quanh true d i qua t a m . cham dan deu ciia vat r ^ n quanh m o t true co' dinh? A. (p = - 4 t ' ( r a d , s). C. cp = 7i/6+4t + 1 5 t ' ( r a d ; s). 2 B. co= 10+ 2t (rad/s; s). D. cp = - 4 t + 2t^ (rad. s). Trong do • m : Kho'i lUcfng dia t r d n dac det (kg). • R: B a n k i n h dia t r o n (m). Van de 3: MOMENLl/C- MOMEN QUAN TINH CUA VATRAN QUAY 5. Vat la h i n h cau dac quay quanh m o t true d i qua t a m . QUANH TRIJC CO DINH I = ^ . m . R^ 5 PHl/OfNG P H A P Trong do I. M o m e n \\ic (M) • m : K h o i luang qua cau (kg). M = F. d • R: B a n k i n h qua cau (m). Trong do: • M : M ome n life ( N . m ) . BAI TAP MAU • F: Lire tae dung (N). • d: Cdnh tay d6n (m). B a i 1 . M o t chat d i e m chiu tdc dung cua mot momen 0,64 N . m l a m chat d i e m (Khoang cdeh tCf true quay den gid eua lire) ehuyen dong t r o n v d i gia toe goc k h o n g doi la 2,5 rad/s^ II. Momen quan tinh a) T i m momen quan t i n h ciia chat diem doi vdi true quay d i qua t a m eiia M = I.y diTcfng t r o n va vuong goc vdi mat phSng chufa dirdng tron. b) T i m kho'i luorng eua chat diem. Biet dudng t r o n cd ban k i n h 20 cm. Trong do: • M : M ome n lire ( N . m ) . Tom tat HUdng dan gidi • I : M o m e n quan t i n h (kg.m^). • M = 0,64 N . m a) M om en quan t i n h eiia chat d i e m do'i v d i true • y: Gia to'e goc (rad/s^). • Y = 2,5 rad/s^ quay d i qua t a m eiia dudng t r o n va vuong gdc I I I . M o m e n q u a n t i n h c u a mpt so' v ^ t r ^ n a) T i m I = ? vdi m a t phSng chufa dudng t r o n . 1. T h a n h c6 t i e t d i | n nho so v d i ehieu dki I quay quanh true d6'i xiJng 1^ b) T i m m = ? M 0,64 M = I.Y ^ ' I = — = duc(ng t r u n g trUc cua t h a n h . Biet R = 20 cm = 0,2 m. 2,5 I = — . m.l' I = 0,256kgm' 12 b) K h o i lugng chat d i e m Trong do 0,256 • m : kho'i lifdng t h a n h (kg) I = niR^ ==> m = 0,2' • /: chieu d a i t h a n h (m) m = 6,4 k g 2. V a t la t h a n h m a n h dong chat kho'i lifcfng m , chieu d a i / cd true quay d i qua mpt dau t h a n h vk vuong goc v d i t h a n h . B a i 2. Mot dia mai chiu tac dung ciia mot life F = 6 N t a i mot diem t r e n v a n h 1=-. m.l^ diem. Biet ban k i n h dia mai la 40 em va dia c6 k hoi liTOng la 2 kg. T i m 3 momen lire va momen qudn t i n h cua dia mai trong ha i triTdng hgrp sau: Trong do a) ^ b) • m : K h o i lucfng t h a n h (kg). • /: Chieu dki t h a n h (m). 3. V a t Ik h i n h t r u rSng hoSc v a n h t r 6 n quay quanh true d i qua t a m . O. M l = m.R' Trong do • m : K h o i lucfng t r u r o n g hoac v ^ n h t r d n (kg). • R: Bkn k i n h t r u r o n g hoac yknh t r 6 n (m).
Tom tat Hu&ng dan gidi b) Gia toe goc cua h# . F = 6 N a) • M o m e n lufc tac dung l e n dia m a i M 60 M = F.d = F.R = 6.0,4 M = Ihf.y ^ Y = y = 625rad/s' • R = 40 cm = 0,4 m 0,096 • m = 2 kg M = 2,4 N . m Tim M = ? I = ? M o m e n quan ti'nh ciia dia m a i B a i 4. Tac dung mot lire co momen k h o n g doi bSng 0,12 N . m l e n chat d i e m ehuyen dong theo quy dao t r o n l a m chat d i e m ehuyen dong c6 gia to'c goc I = - m.R' = i . 2 . 0 , 4 ' 2 2 y > 0. K h i y t a n g 1 rad/s^ t h i momen quan t i n h ciia chat d i e m doi v d i true I = 0,16kg.m' quay g i a m 0,02 kgm^. T i m gia toe goc ciia chat diem. b) » Momen life tac dung l e n dia m a i Tom tdt Hiidng ddn gidi M = F.d = F.R.sina o M = 6.0,4.sin30" M = 1,2 N . m . M = 0,12 N . m • Ta co: • M o m e n quan t i n h cua dia m a i . y> 0 Luc dau: M - I.y (1) 0) • niA 100 g = 0,1 kg. niA • mu = 300 g = 0,3 k g . • M = 60 N . m . GE BAI TAPTRAC NGHIEM A B Tim irithanh C a u 20. M o t dia t r o n mong, phang, dong chat co the quay xung quanh 1 true d i a) I h , = ? b) y = ? qua t a m va vuong goc v d i m a t p h ^ n g dia. Tac dung vao dia m o t liTc co a) Momen quan t i n h ciia he phiicfng t i e p tuyen v d i v a n h dia co dp Idn la 40 N . B i e t ban k i n h v a n h dia la Ihe = Ithanh + + 1B 40 cm. D i a ehuyen dong quanh true v d i y = 2 rad/s^. Bo qua m o i siJe can. 1 Iihanh = - ;2 mthanh-/' = — .0,6.0,8^ = 0,032 k g m l K h o i lirong cua dia la ^ Iz 0,8 A. 100 k g B. 200 k g C. 300 k g D. 400 k g • IA = HIA-RA^ = niA = 0,1 = 0,016 kgm^ {2j C a u 21. M o t r o n g roc co ban k i n h 10 em va co momen quan t i n h d o i v d i true 2 / quay la 0,04 kgm^ ban dau r o n g roc diing y e n , tae dung vao r o n g roe mot lire 0,8 • I B = mB.Rn^ = me. = 0,3. = 0,048 kgm^ k h o n g doi F = 6 N t i e p tuyen v d i v a n h ngoai cua no. Bo qua m o i sufe can. .2, v Gia toe goc ciia r o n g roc la Vay Ihe = 0,032 + 0,016 + 0,048 -> I,,^ = 0,096 (kgm^) A. 5 rad/s'. B. 10 r a d / s l C. 15 rad/s^ D. 20 r a d / s l
C a u 2 2 . M o t t h a n h A B d o n g c h a t c6 t i e t d i # n n h 6 so v d i c h i e u d ^ i I . B i e ' t t r u e C S u 3 0 . M o t d i a t r 6 n khS'i l i r o n g m = 1 k g , hAn k i n h 20 c m q u a y x u n g quanh q u a y d i q u a t r u n g d i e m t h a n h v a v u o n g goc v d i t h a n h . M o m e n l y e l a m q u a y m o t t r u e ( A ' ) song song v a each true d o i xiJng ( A ) cua d i a k h o a n g 4 cm. t h a n h n h a n h d S n d e u l a 0,5 N . m . B o q u a m o i liifc c a n . T h a n h d a i 4 0 c m , M o m e n q u d n t i n h ciia d i a d o i v d i t r u e ( A ' ) l a nang 100 g. To'c do goc c u a t h a n h sau k h i t h a n h bMt d a u q u a y d u g c 4s tilf A. 0,016 k g . m ' . B. 0,0326 k g . m ' . C. 0,0016 k g . m ' . D . 0,0216 k g . m ' . t r a n g t h a i diJng y e n l a C a u 3 1 . M o t d i a t r o n ed k h o i l i / d n g m = 1 k g b a n k i n h 2 0 c m c h i u t a c d u n g eiia A. 1500 rad/s. B . 1600 rad/s. C. 7 5 0 r a d / s . D . 400 rad/s. luc F t i e p t u y e n v d i v a n h d i a , d p I d n F = 1 N . M o m e n q u a n t i n h eiia d i a v a C a u 2 3 . T a c d u n g 1 l u c c6 m o m e n hkng 1,6 N . m l e n c h a t d i e m c h u y e n dpng m o m e n lire d o i v d i t r u e q u a y q u a t a m 1^ t h e o q u y d a o t r o n l a m c h u y e n d o n g c6 g i a to'c goc y > 0. K h i y g i a m 4 A. 0,02 k g . m ' ; 0 , 1 N . m . C . 0 , 0 3 k g . m ' ; 0,2 N . m . rad/s^ t h i m o m e n q u a n t i n h c u a c h a t d i e m d o i v d i t r u e q u a y t a n g 0,2 k g . m ^ . B . 0 , 0 2 k g . m ' ; 0,2 N . m . D . 0 , 0 4 k g . m ' ; 0,2 N . m . G i a t o e goc c u a c h a t diem A. 8 r a d / s l . B. 6 rad/sl C. 4 r a d / s l D. 2 rad/sl C a u 3 2 . M o t d i a t r o n ed k h o i l U d n g m = 2 0 0 g b a n k i n h R = 2 0 e m d a n g q u a y C a u 2 4 . M o t q u a c a u c6 k h o i l i i p n g 5 0 0 g q u a y q u a n h m o t t r u e d o i x i J n g . Q u a v d i t o e d p gdc 2 0 r a d / s t h i b i m o t lire c a n F^ ed d p I d n k h o n g d o i t i e p x i i c v d i cau CO b a n k i n h l a 10 c m . M o m e n q u a n t i n h c i i a q u a c a u d a c q u a y q u a n h t r u e v ^ n h t h e o p h u d n g t i e p t u y e n v a dCfng l a i s a u t h d i g i a n t = 2 0 s. D p I d n l u c di qua tarn l a can tac dung l e n v a n h d i a l a A . 10"^ k g . m ^ B . 210"^ k g . m l C. 3.10"^ k g . m l D . 4.10"^ k g . m ' . A. 0,01 N . B . 0,03 N . C . 0,04 N . D . 0,02 N . C a u 25. M o t d i a t r o n b a n k i n h 20 c m k h o i lUdng 2 k g quay q u a n h 1 t r u e n ^ m n g a n g q u a k h o i t a m 0 ciia d i a . T a c d u n g Van de 4: BAI TAP VE PHL/ONG TRJNH CHUYEN DQNG CUA VAT 2 lye eung chieu F , , F j tiep xuc v d i v a n h d i a t a i 2 dau RA N QUA Y QUANH MQ T TRUC d u d n g k i n h A B v a c6 d p I d n F i = I O N , = 12N nhu hinh PHL/OfNG PHAP ve. G i a to'c goc c u a d i a l a C d c cong thiiCc A. 8 r a d / s l B. 9 rad/s^ Chuyen dpng thgng C. 10 r a d / s ' . D. 11 r a d / s l Quay bien doi d e u bien doi d e u C a u 2 6 . M o t t h a n h A B ed k h o i l i f d n g 1 k g , / = I m . H a i d a u g ^ n 2 v i e n b i n h o • F,, = m . a • M = I. y ; M = F. d CO k h o i iMng hkng n h a u . Bie't m o m e n q u a n t i n h c u a h p d o i v d i d i i d n g t r u n g • Liiu y true l a 11/60 k g . m ' . K h o i l u p n g m o i v i e n b i l a V d i : F,„ = F, + F , + ... Q u a y theo c h i e u (+) A . 100 g. B . 2 0 0 g. C. 3 0 0 g. D . 4 0 0 g. => M = F . d C a u 2 7 . M o t b d n h x e ed m o m e n q u d n t i n h d o i v d i t r u e q u a y eo d i n h l a 4 k g . m ' , Q u a y ngUde c h i e u (+) d a n g d i J i i g y e n t h i c h i u t a c d u n g ciia m o t m o m e n l u c 3 0 N . m doi v d i true =^ M = - F . d , ( 0 = (OQ + y . t q u a y . B o q u a m o i l u c c a n . S a u b a o l a u , k e tCr k h i hit d a u q u a y , b d n h x e d a t t d i t o e d p goc 7 5 r a d / s ? • V = Vo + at , 9 9o = Wot + ^ . at^ A . 10 s. B . 1 1 s. C. 12 s. D . 2 0 s. • S = Vot + ^ , 0)^ - (Oo = 2 Y ( I P - ( P O ) C a u 2 8 . H a i b a n h x e A v a B ed c u n g d p n g n S n g q u a y , t o e d p gdc co^ = 8CO3. Ti • Vt' - Vo' = 2a.s • a = Vaf, + a? so m o m e n q u a n t i n h ~ d o i v d i t r u e q u a y d i q u a t a m c u a A v a B c6 g i d t r i Ik an = .r, at = r. y A . 8. B. 64. C . 1/64. D . 1/8. C a u 2 9 . M o t q u a c a u k h o i l u p n g m = 5 0 0 g, b a n k i n h R = 10 e m diTdc t r e o hkng m o t s d i d a y m a n h mk k h o a n g e a c h til d i e m t r e o d e n t a m q u a c a u l a I m . M o m e n q u a n t i n h c i i a q u i e a u d o i v d i d i e m t r e o Ik A. 0 , 5 0 2 k g . m ' . B . 0,45 k g . m ' . C. 2.10"' k g . m ' . D . 0,326 k g . m ' .
BAI TAP MAU 1 B^ a i 2. H a i vat m , = 2 k g , m2 = 2 k g dUcfc l i e n k e t v d i nhau b&ng mot day nhe, k h o n g dan, v ^ t qua mot r d n g B a i 1. M o t t h i i n g nxidc dugc tha xudng gieng nhcJ roc CO ban k i n h 8 cm va momen quan mot soi day d a i quan quanh h i n h t r u c6 ban k i n h t i n h la 0,04 kgm^. B i e t day k h o n g R = 10 cm va momen quan t i n h I - 0,02 kgm^. O trUOt t r e n r o n g roc n h u l i g k h o n g biet K h o i lu'ong ciia day va momen quan t i n h cua tay giiJa v a t m2 va ban c6 ma sat hay quay k h o n g dang ke. H i n h t r u coi n h a tay quay khong. Luc dau eac vat duoc giii' duTng t y do k h o n g ma sat quanh mot true c6 d i n h . Kho'i yen, sau do he vat ducfc t h a ra. NgUdi ta t h a y r a n g sau k h o a n g t h d i gian la iMng t h u n g nUdc la 8 k g . T i n h : 4 s t h i r o n g roc quay quanh true cua no ducfc 3 vong. B i e t gia toe cua cac a) Gia toe eiia t h i j n g niidc. vat m i va m2 khong doi. Bo qua ma sat d true cua rong roc. Lay g = 10 m/s^ b) Luc cang day treo. Cho g = 10 m/s^. a) T i n h gia toe goe cua r o n g roc. b) T i n h gia toe eiia m j va m^. Tom tat Hiidng dan gidi c) T i n h lire cang day d h a i ben cua r o n g roc. • R = 1 0 c m = 0,1 n i . Nhaii xet: T r o n g bai tap nay, chung t a can xac d) Co ma sat giiTa v a t m2 va m a t san hay khong? Neu cd, hay t i n h he so • ! = 0,02 k g m l d i n h duoc v a t nao chuyen dong quay quanh ma sat giiifa m2 va m a t san. • m = 8 kg. true va v a t nao chuyen dong t i n h t i e n . • g = 10 m/s^. T r o n g b a i toan nay, chung ta t h a y r a n g r o n g Tom tat Hitdng dan gidi Tinh: rpc CO chuyen dong quay va t h u n g n U d c t h i • n i l = 2 kg. a) Gia tdc gdc cua r o n g roc. a) a = ? b) T = ? chuyen dong t i n h t i e n . • m2 = 2 kg. Nhau xet: T r o n g t h d i gian 4 s r o n g roc quay 3 • R = 8 cm. vong a) A p dung d i n h luat I I N i u t o n cho t h i j n g n U d c va phuang t r i n h dong lire hoc • I = 0,04 k g m ^ cho chuyen dong quay ciia h i n h t r u . N = • (Or, = 0. 2TI Ta c6: • t = 4 s - > N = 3 vong. - » cp - (pi, = N.27t = 3.271 = 671 rad * Doi v d i t h i j n g nude. • g = 10 m/s^. A p dung cong thdc P-T-m.a (1) a) y = ? b) a i = ? a. = ? (p - (PO = 0)0.t + 6n = 0.4 + * Doi vdi h i n h t r u . c) T i = ? T 2 = ? y = 0,7571 ( r a d / s ' ) M - ly T.R = I.y d) Cd ma sat giufa m2 va ma he thufc l i e n he giuTa gia t o e dai b) Gia tdc cua n i i va m2 san khong? Neu cd ai = a2 = at t i n h he so ma sat va gia toe goe la a = R.y y= — ma a, = R.y = 0,08.0,75Tt = 0,1884 m/s^ (+) R a, = a„ = 0,1884 m/s" La -> T.R - I . - T (2) R^ e) Lire cSng day d h a i ben true r o n g roc N2 R Nhau xet: Chieu (+) cua cac v a t nhir h i n h . Cong (1) va (2) => P = ma + tLtl. R^ • Lire cang day T| m2 *Xetvatmi: Pi - T , = m i . a i mg 8.10 o mg = m +• a o a = a = 8(m/s') m,g - T i = miai Ti 0,02 c=> 2.10 - T, = 2.0,1884 Pz fi o T, = 19,6232 (N) b) Lyc cang day treo. * Xet r o n g roe: nil (+) The a = 8 mJs^ vao (2) Ta c6: M , + M2 = ly o T i . R - T2R = ly la 0,02.8 (2) ^ T = T = 1 6 (N) T2 = 18,4457 (N) R^ 0,1^ » 19,6232.0,08 - T2.0,08 = 0,04.0,75Tt
d ) Nhdn xet: C o n g (4), (5), ( 6 ) • T2 = 1 8 , 4 4 5 7 ( N ) P, - P2 = m i a + m2a + (7) • m2a2 = 2 . 0 , 1 8 8 4 = 0 , 3 7 6 8 ( N ) R D o T2 > m2a2 n e n giOfa m2 v a m a t s a n c6 lire m a s a t - > L i i c n ^ y lire m a s^t M a t k h a c t a l a i co at = a i = 82 = a = Ry giOra m2 v a s a n ngiroc h u d n g v 6 i T2 nhxi h i n h ve b e n d u d i . D o N2 c a n b k n g P2 n e n t a c6: N2 T2 - F „ „ = m2a2 (*) ma = ^N2 = 1.1.P2 = i-imag (do N2 = P2) T h e (8) v a o ( 7 ) t a eo: (7) ( m i - m2)g = ( m i + ma + •)a R= n e n t i f (*) ->• T2 - |im2g = m2a2 18.4457 - n.2.10 = 2.0.1884 (m, -m,)g a = H = 0,9034 »2 R / B a i 3. C h o co h e n h i f h i n h v e : R o n g r o c c6 k h o i liTcfng 14 k g , b a n k i n h 10 c m . H a l v a t m i = 600 g Vdi I = i m , , . R ' = i . 1 4 . 0 , 1 - = 0,07 kgm' 2 2 v a m2 = 4 0 0 g diTcfc t r e o v a o r o n g r o c n h d day k h o n g d a n , k h o i lucfng d a y k h o n g d a n g k e . ( 0 , 6 - 0 , 4 ) . 10 Nen a - a = 0,25m/3^ = = a. R D a y k h o n g trucrt t r e n r o n g roc v a r o n g roc c6 t h e 0 , 6 . 0 , 4 . ° ^ ^ quay q u a n h m o t true n k m n g a n g . B a n dau h a i v a t dUOc giU dutog y e n r o i sau do b u o n g n h e cho he T h e a = 0,25 m/s^ v a o ( 8 ) y = |- = y = 2,5(rad/s') chuyen dong. Cho g 10 m/s^ a) T i m g i a t o e gdc cua r o n g r o c v a g i a t o e eiia 2 K 0,1 v a t m i , m2^ b) L u c c a n g d a y t r e o d h a i b e n r o n g roc b ) T i m lue c a n g cua d a y t r e o h a i b e n r o n g roc. (4) - > m i g - T i = m i a c) T i m q u a n g d u d n g m a m i , m2 d i d u o c sau 2 s mi m2 T, = 5,85 ( N ) k e tii lue t h a cho h e c h u y e n d o n g v a goe ma r o n g roc quay duac sau 2 s t r e n . (5) - m 2 g + T2 = m2a T„ = 4 , 1 ( N ) Tom tat HUafng dan gidi • TCirr = 14 kg Nhan xet: c) • Q u a n g . d u 6 n g m , , m2 d i d u o e s a u 2 s k e tii l i i c t h a cho h $ c h u y e n dong. • R = 10 c m = 0 , 1 m Do Pi = m , . g = 0,6.10 = 6 N Nhan xet: D o d a y k h o n g d a n n e n q u a n g d u d n g m i , m2 d i l a b ^ n g n h a u . • m , = 6 0 0 g = 0,6 k g P2 = m 2 g = 0 , 4 . 1 0 = 4 N P , > P2 at^ • m2 = 4 0 0 g = 0,4 k g Vat m i , m2, r o n g roc co ehieu chuyen S = vo.t + (9) a) T i m y = ? a i = ? a 2 = ? d o n g c u n g c h i n h l a c h i e u ducfng d a chon b) T , = ? T i = ? t r e n n h u h i n h ve. V d i vo = 0 e) S i = ? S2 = ?; (p - (Po = ? t = 2 s 0 2 5 2^ a) Y = ? a i = ? 32 = ? (9) S = 0.2 + = 0,5 m • Xet mi: Pi - T i = mjai (1) S, = 8 2 = S = 0 , 5 ( m ) m2: - P 2 + T2 = m2a2 (2) R o n g r o c : M , + M2 = l y T i . R - T2.R = l y • Goe m a r o n g r o c q u a y dUcfc t r o n g 2 s T i - T2 = (3) T2 T, (p -
B a i 4. M o t b a n h xe chiu tdc dung cua m p t momen lire M , c6 dp Idn k h o n g doi. T r o n g t h d i gian 5 s dau toe dp goc ciia b a n h xe tSng deu tii 0 d e n 10 cp - (po = 0),,^ . t i + 2 rad/s. Sau do momen M , ngifng tac dung, b a n h xe quay cham d a n deu 2.5^ ditog h d n sau 20 s ke tCf lue M j ngCrng tae dung. B i e t r k n g t r o n g qua t r i n h (p - cpo = 0.5 + = 25 r a d quay t h i b a n h xe luon ehiu tdc dung ciia momen lye m a sat k h o n g d o i va CO dp Idn l a 10 N . m Vay tii (•) N = f ^ = 3,98(v6ng) a) T i n h gia toe goc cua b d n h xe t r o n g h a i giai doan quay n h a n h d a n deu 2.71 va quay eham dan d i u . b) T i n h momen quan t i n h eua b a n h xe d o i v d i true quay va momen life M j . BAI TAPTRAC NGHIEM c) T i m so vong ma banh xe quay dupe trong giai doan quay nhanh dan deu. C a u 3 3 . Cho m o t b a n h xe ehiu tdc dung ciia m o t momen lUc M i k h o n g d o i . Tom tdt Tong cua momen M i va momen lire m a sdt e6 g i d t r i b k n g BON.m. T r o n g 2s HUdng dan gidi dau, toe dp goc cua b a n h b i e n d o i deu tii 0 rad/s d e n 10 rad/s. Sau do momen • Giai doan I Giai doan I Giai doan I I M l ngi/ng tac dung, b d n h xe quay cham d a n deu v^ difng h ^ n l a i 50s. G i a suf ti = 5 s momen lire m a sat l a k h o n g d o i t r o n g suot t h d i gian b a n h xe quay. Dp I d n momen life m a sat la (Oi = 10 rad/s A. 12 N . m . B. 2 N . m . , C. 3 N . m . D. 4 N . m . / 0 ^ • Giai doan I I . C a u 3 4 . Cho m p t b a n h xe chiu tac dung ciia m o t momen lire M i k h o n g d 6 i . • • J t2 = 20 s Tong eua momen M i va momen life m a sat cd gia t r i b k n g 18N.m. T r o n g 4 s (0,,^ = 10 rad/s dau, toe dp goc cua b a n h xe b i e n d o i deu ti^ 0 rad/s den 12 rad/s. Sau d6 k momen M i ngii'ng tac dung, b a n h xe quay cham d a n deu v a dCfng h ^ n l a i 24s. 0)2 = 0 Gia sijf momen luc m a sat l a k h o n g d o i t r o n g suot t h d i gian b d n h xe quay. • I M,„31 = 10 N . m F ins Momen liic M J a a) T i m yi = ? = ? A. 20 N . m . B. 21 N . m . C. 22 N . m . D . 23 N . m . "o, =0 (OQ, = 10 rad/s b) T i m I = ? M l = ? C a u 35. M p t b a n h xe n h a n dupc m p t gia toe goc 2 rad/s^ quay n h a n h d a n deu c) N , = ? CO] = 10 rad/s 2= 0 ti^ t r a n g t h a i dUng y e n t r o n g 4s dudi tac dung eiia momen life M j v^ momen ti = 5 s t2 = 20 s liie m a sat. Sau do momen lUc M i ngUng tac dung t h i b a n h xe quay c h a m a) Gia toe gde eiia b a n h xe t r o n g giai doan I (quay n h a n h dan deu) dan deu va difng l a i sau 10 vong quay. Toe dp gde sau 4s va t h d i gian tii liic -'"o, 10-0 b a n h xe b^t dau quay cho den k h i diing l a i l a Yi = y, = 2 ( r a d / s ' ) t, A. 8 rad/s; 19,7 s. B. 9 rad/s; 12,3 s. Gia toe goc ciia b a n h xe t r o n g giai doan I I (quay cham dan deu) C. 8 rad/s; 12,3 s. D . 9 rad/s; 11,3 s. CO, - (0 0, 0-10 C a u 3 6 . M p t b a n h xe c6 k h o i lupng 2 k g va b a n k i n h 20 cm quay n h a n h d a n 72 = Y2 = -0,5 r a d / s ' deu tii t r a n g t h a i ddng y e n va sau 4 s d a t toe dp gde l a 40 rad/s. B i e t r l i n g t^ 20 t r o n g 4 s n a y v a t chiu tac dung cua life F va liTc m a sat theo phupng t i e p b) Momen quan t i n h cua b a n h xe d o i v d i true quay va momen M i • Tim I : tuyen b a n h xe. Sau 4 s t r e n luc F m a t d i , b a n h xe quay cham d a n deu diTcfc Xet giai doan r o n g roe quay cham dan deu 10s t h i dCmg l a i . Dp I d n cua lUc F tdc dung l e n b d n h xe \k A. 0,7 N . B. 1,4 N . C. 2,8 N . D. 3,6 N . M „ , = Iy2 - > - 1 0 = I . ( - 0 , 5 ) ^ I = 2 0 k g m ' ' Tim M i : C a u 3 7 . M p t m a y A - t i i t dung de n g h i e n cUu chuyen Xet giai doan r 6 n g roc quay n h a n h dan deu. dpng cua cac v a t . C6 k h o i lupng khac nhau n h i i h i n h . Cho m i = 1 k g , m2 = 3 k g r b n g rpe quay M l + M„,, = l y i ^ M l - 10 = 20.2 = 50 N . m quanh m p t true n k m ngang. Gia t h u y e t spi day c) So r o n g roe m a b a n h xe quay dupe t r o n g giai doan quay n h a n h dan deu k h o n g dan va k h o n g trUpt t r e n r o n g roc. Cho kho'i Ni = ^ (*) lupng r o n g rpe la 2 k g , r = 10 em. Cho g = 10 m/s^. 271 Gia toe m o i v a t m i va m2 l a V d i goc quay ma rong roc quay dupc trong giai doan I (quay nhanh dan deu) A. 1 m / s l B. 2 m / s l ' C. 3 m / s l D. 4 vols
C a u 38. M o t dia dac ban k i n h 0,25 m c6 the quay quanh mot true doi xiJng d i BAI TAP MAU qua t a m eua no. M o t soi day m a n h nhe dUdc quan quanh v a n h dia. ngudi t a keo dau sgi day b k n g m p t life k h o n g d o i 12 N . H a i giay sau ke tix lue tdc B a i 1 . M p t dia m a i eo k h o i lupng 2 k g , ban k i n h la 14 cm quay t r o n deu dung lire l a m dia quay v d i to'c do g6c b ^ n g 20 rad/s. Gia toe goe eua dia va quanh true doi xuTng d i qua t a m dia v d i to'c dp goe la 1200 vong/phiit. T i m gia toe eiia dau day la momen quan t i n h va momen dpng liipng eiia dia m a i t r o n g sU quay quanh A. 10 rad/s^; 2,5 m / s l C. 12 rad/s^ 4 m / s l true cua no. , B. 11 rad/s'^; 3 m/s^. D . 10 rad/s^ 3 m / s l C a u 39. M o t dia dac b a n k i n h 0,25 m c6 the quay quanh mot true d o i xvJng d i Tom tat HUc/ng dan gidi qua t a m cua no. M o t soi day m a n h nhe du'cfc quan quanh v a n h dia, ngxXdi ta m = 2 kg. M o m e n quan t i n h ciia dia m a i keo dau soi day b k n g m p t liic k h o n g doi I O N . B o n giay sau ke tii luc tde R = 14 cm = 0,14 m . I = i m . R 2 = - .2.0,14^ dung life t h i dia quay v d i to'c dp g6c hkng 40 rad/s. Cho g = 10 m/s^. Goc quay CO = 1200 vong/phut. 2 2 dupe ciia dia va c h i l u d ^ i doan day difpc keo la I = 0,0196 kgm= = 1 2 0 0 . ^ . A. 40 r a d ; 5 m . B. 80 r a d ; 20 m . 60s • M o m e n dpng lupng cua dia m a i t r o n g sir qiiay C. 80 r a d ; 4 m . D. 40 r a d ; 10 m . = 40Tt rad/s. quanh true ciia no C a u 40. M p t v a t n a n g 90 N diipc bupc vao dau 1 spi day nhe quan quanh 1 Tim I = ? L = I.co = 0,0196.4071 r o n g roc dac c6 b a n k i n h 0,2 m , k h o i liipng 2 k g . Rong roe c6 true quay co L = ? L = 2,46176 k g m ' / s d i n h nkm ngang va d i qua t a m cua no. N g i i d i ta t h a cho v a t r p i t i i dp cao h xuong dat. Cho g = 10 m/s^. Luc c&ng eua day va gia toe cua v a t l a B a i 2. M p t banh xe chiu tac dung eua m p t momen k h o n g d o i n e n quay n h a n h A. 9 N ; 4 m / s l B. 9 N ; 9 m / s l C. 4 N ; 6 mJs\. 4 N ; 9 m / s l dan deu k h o n g to'c dp goc lue dau va sau 5 s t h i toe dp goc eua b a n h xe la 20 rad/s. B i e t m o m e n quan t i n h cua b d n h xe doi v d i true quay cua n6 1^ Van de 5: MOMEN DQNG LU0NG D!NH LUAT BAO TOAN MOMEN 0,4 kgm/s^. T i m momen dpng lupng cua b a n h xe t a i t h d i d i e m 8 s. DQNG LU0NG Tom tat Hitcfng dan gidi PHl/dNG PHAP • lOo = 0 Nhan xet: Do b a n h xe quay n h a n h dan deu n e n •t = 5 s gia toe cua b d n h xe k h o n g d o i . I. M o m e n d p n g liitfng • M = 20 rad/s • Gia toe cua b a n h xe. L = I.M • I = 0,4 kgm^ (1) - C O n 20-0 Y= = 4 rad/s' Trong do t 5 T i m L = ? Luc t = 8 s. • L : M o m e n dpng lupng (kg.mVs). • To'c dp goc eua b d n h xe t a i t h & i d i e m 8 s • I : M o m e n quan t i n h (kg.m^). (0 = coo + y.t = 0 + 4.8 = 32 rad/s • co: V a n toe toe (rad/s). • M o m e n dpng iMng eua b a n h xe t a i t h d i d i e m t = 8 s I I . D i n h l u $ t b a o t o a n m o m e n d p n g li^dng L = I.co = 0,4.32
• (Oi = 2 5 r a d / s « 0. C a u 4 6 . M o t s ^ n q u a y h i n h t r u dSc c6 k h o i l u g n g M = 2 0 0 k g , b d n k i n h R = 2 m Ithanh = — I".Z . r = 0,2 m d m e p s a n cd 1 v a t k h o i l u o n g 4 k g . S a n q u a y d e u v d i co = 20 r a d / s . M o m e n L u c nky t a c h i x e t v a t c6 m = 1 kg long vao Tim C02 = ? dong l u p n g ciia he l a t h a n h v a c6 t h e trugt t r e n t h a n h . A. 6340 k g m ' / s . B. 7320 k g m ' / s . C. 8 0 0 0 k g m ' / s . D . 8 3 2 0 kgm^'/s. A p d u n g d i n h l u a t b^o t o ^ n m o m e n d p n g l u o n g . C a u 4 7 . M o t v a t cd m o m e n q u a n t i n h 0,72 k g . m ^ q u a y d e u 10 v o n g t r o n g 2s. L i = L2 (A) M o m e n d o n g l U t f n g c u a v a t cd do I d n hhng I i C O i = I2CO2 (1) A . 40,5 kg.m^/s. B. 30,608 kg.m^/s. Vdi I i = mR? (2) R 2 = 0,2 m vat thanh C. 2 0 , 5 k g . m ^ / s . D. 22,608 kg.m^/s. l2 = mR^ (3) A— C a u 4 8 . M o t n g U d i d d n g t r e n g h e d a u G i u e o ' p s k i c a m 1 b a n h xe cd t r u e q u a y T h e (2). (3) v^o (1) UC UB t h ^ n g d d n g . N g U d i a y d a y cho b a n h xe q u a y v d i v a n td'c 6 0 v d n g / p h u t t h i (1) ^ m R j .0)1 = m R j .0)2 ngu'di a y se c h u y e n d o n g n h u t h e n a o ? V d i v a n toe hkng bao n h i e u ? B i e t 0,4 m R i = 0,4 m m o m e n q u a n t i n h c i i a n g u d i d o i v d i t r u e q u a y l a I = 2 k g m ^ v a c i i a b a n h xe - - 0'4^25 R 0,2^ do'i v d i t r u e q u a y l a I = 1 k g . m ^ A . N g U d i a y c h u y e n d o n g c i i n g c h i e u q u a y c u a b a n h xe v d i v a n t o e gdc l a 2 0 = lOOrad/s vong/ phut. B . N g u d i a y c h u y e n d o n g ngi/cfc c h i e u q u a y c i i a b a n h xe v d i v a n toe gdc 1^ 2 0 BAI T A P T R A C N G H I E M vong/ phiit. C. N g u d i a y c h u y e n d o n g c i i n g c h i e u v d i v a n td'e gdc l a 3 0 v d n g / p h u t . D . N g U d i a y c h u y e n d o n g n g u p c c h i e u v d i v a n toe gdc l a 3 0 v d n g / p h u t . C a u 4 1 . M o t d i a m a i c6 m o m e n q u a n t i n h d o i v d i t r u e q u a y c u a n o l a 0,5 k g . m ^ . D i a c h i u m o t m o m e n life k h o n g d o i l a 2 N . m n e n b ^ t d a u q u a y n h a n h d a n d e u C a i i 4 9 . M o t t h a n h A B d a i I m cd k h d ' i li/cJng k h o n g d a n g k e . 6 m o t dau ciia v d i toe do goc luc d a u cOg = 0 . M o m e n d o n g liTpng ciia d i a t a i thcfi d i e m 10s l a t h a n h , n g U d i t a g a n v a t m = 0,2 k g l o n g v a o t h a n h v a cd t h e t r i f o t tren t h a n h . L u c d a u v a t d d a u t h a n h v a t h a n h d a n g q u a y d e u v d i td'c dp gdc A . 40 kg.m^/s. B. 80 kg.mVs. C. 20 k g . m ^ / s . D . 2 4 0 k g . m V s. 0) = 20 r a d / s q u a y q u a n h t r u e do'i x i i n g . S a u do v a t t r u p t d e n v i t r i e a c h t r u e C a u 4 2 . C o i T r a i D a t l a m o t q u a c a u d o n g c h a t c6 M = 6.10^'' k g , R = 6 4 0 0 k m . q u a y 0,25 m . T o e dp gdc c u a v a t l u c n a y l a C o i T r a i D a t q u a y t r o n d e u 2 4 g i d dUdc 1 v o n g . M o m e n d o n g l i f d n g c u a T r a i A . 80 r a d / s . B . 100 r a d / s . C. 2 0 0 r a d / s . D . 500 rad/s. D a t t r o n g sif q u a y q u a n h t r u e c i i a n o l a A. 6,28.10''kg.m'/s. B . 5,56. l O ' ^ k g . m ' / s . C. 7 , 1 4 . 1 0 ' " k g . m V s . D . 5,83.10^' k g . m ' / s . Van de 6: DQNG NANG. DINH LI DQNG NANG CUA VATRAN CO C a u 4 3 . M o t d i a dac c6 b a n k i n h R, d i a c6 t h e q u a y x u n g q u a n h t r u e d o i xiJrng TRI^C QUAY CO DINH d i q u a t a m v a v u o n g goc v d i m a t p h ^ n g d i a . D i a c h i u t a c d u n g c i i a 1 m o m e n PHU'GfNG PHAP life k h o n g d o i M = 5 N . m . Sau 2 s k e t i f l u c b d t d a u q u a y , t o e do goc c i i a d i a I. Dpng nang quay l a 30 r a d / s . M o m e n d o n g lUcfng c i i a d i a t a i t h d i d i e m 3 s l a W,, = - . W A. 4 kgm^/s. B . 15 k g m ^ / s . C. 6 k g m ^ / s . D. 7 kgm^/s. '' 2 C a u 44. M o t t h a n h n h e d a i I m quay deu t r o n g m a t p h a n g n g a n g x u n g q u a n h Trong do: t r u e t h a n g diirng d i q u a t r u n g d i e m c i i a t h a n h . H a i d a u t h a n h c6 2 c h a t d i e m • W , i : D o n g n S n g quay (J). k h o i l U d n g 2 k g v a 1 k g . V a n toe cua m o i c h a t d i e m l a 5 m / s . M o m e n dong • I : M o m e n q u a n t i n h (kg.m^). l i / a n g cua t h a n h l a , CO: V a n td'c gdc ( r a d / s). A . 10,5 k g . m ^ / s . B . 11,5 k g . m ^ / s . C. 12,5 k g . m ' / s . D . 7,5 k g m ^ / s . II. Djnh li dong ndnq C a u 4 5 . M o t t h a n h A B cd k h o i luang 1 k g , chieu dai 2 m , 2 dau t h a n h g^n 2 v i e n b i n h o m o i v i e n cd k h o i l u a n g l a 100 g. M o m e n d o n g lugrng c i i a t h a n h k h i t h a n h q u a y v d i co = 4 0 r a d / s l a Trong do: • Angi : C o n g n g o a i l u c ( J ) . A . ^0,2 k g m V s . B . 2 1 , 2 kgm^/s. C. 2 2 , 2 k g m V s . D. 23,2 k g m/s. » A : Dp b i e n t h i e n d o n g n S n g (J).