# Makeup Exam #1

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## Makeup Exam #1

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M1) Assuming that it takes 0.10 s for the driver to react before applying the brakes, what is the stopping distance (the distance from the point where the driver first sees the need to stop to the point where the car comes to a stop) for a car traveling at 25 m/s if the deceleration due to the brakes is 3.5 m/s2? A) 174 m B) 87 m C) 186 m D) 92 m 2) An astronaut stands by the rim of a crater on the moon, where the acceleration of gravity is 1.62 m/s2. To determine the depth of the crater, she drops a rock and measures...

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## Nội dung Text: Makeup Exam #1

1. Makeup Exam #1 Name: MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Assuming that it takes 0.10 s for the driver to react before applying the brakes, what is the stopping distance (the distance from the point where the driver first sees the need to stop to the point where the car comes to a stop) for a car traveling at 25 m/s if the deceleration due to the brakes is 3.5 m/s 2? A) 174 m B) 87 m C) 186 m D) 92 m 2) An astronaut stands by the rim of a crater on the moon, where the acceleration of gravity is 1.62 m/s 2. To determine the depth of the crater, she drops a rock and measures the time it takes for it to hit the bottom. If the depth of the crater is 120 m, how long does it take for the rock to fall? A) 3.04 s B) 29.3 s C) 32.1 s D) 12.2 s 3) A projectile is launched with an initial velocity of 80 m/s at an angle of 30e above the horizontal. Neglecting air resistance, what is horizontal component of the projectile's acceleration? A) 80 m/s 2 B) 4.9 m/s 2 C) 0 m/s 2 D) 9.8 m/s 2 4) A boy kicks a football with an initial velocity of 28.0 m/s at an angle of 60.0e above the horizontal. What is the highest elevation reached by the football in its trajectory? A) 27.9 m B) 30.0 m C) 28.2 m D) 31.5 m 1
2. 5) A net force of 120 N is applied to a certain object. As a result, the object accelerates with an acceleration of 24.0 m/s 2. The mass of the object is A) 0.200 kg. B) 5.00 kg. C) 2880 kg. D) 144 kg. 6) A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the locomotive has a mass of 80,000 kg, the next one, 50,000 kg, and the last one, 70,000 kg. Neglect friction. What is the force between the 50,000-kg and 70,000-kg wagons? A) 35,000 N B) 65,000 N C) 40,000 N D) 60,000 N 7) In the figure below, the block of mass m is at rest on an inclined plane that makes an angle q with the horizontal. The force of static friction f must be such that A) f > mg. B) f = mg sinq. C) f > mg cosq. D) f = mg cosq. 2
3. 8) Compare the two situations shown in the figure below. On the left (A), James is holding the rope and keeping the bucket at rest. On the right (B), James ties the rope to the bucket so that it keeps the bucket at rest. In both cases the bucket contains the same quantity of water. In what case is the tension in the rope higher? A) left B) right C) It is the same in both cases. D) need more data to answer Figure 6-4 9) Refer to Figure 6-4. Block A has a mass of 2.00 kg and rests on a rough table and is connected to block B, which has a mass of 3.00 kg, after passing over an ideal pulley, as shown. Block B is released from rest. The coefficient of kinetic friction between block A and the table is 0.300. What is the acceleration of the masses? A) 3.92 m/s 2 B) 5.89 m/s 2 C) 6.54 m/s 2 D) 4.71 m/s 2 3
4. Figure 6-3 10) A 10-kg sign is held by two ropes as shown in Figure 6-3. What is the tension on rope A? A) 69 N B) 72 N C) 98 N D) 88 N 4
5. Makeup for Exam #1 Part 2: Partial Credit 1. A basketball player runs down the court, following the path indicated by the vectors A, B, and C in the figure. The magnitudes of these three vectors are: A = 10.0 m, B = 20.0 m, and C = 7.0 m . Find the magnitude and direction of the net displacement of the player using (a) the graphical method and (b) the component method of vector addition. A 0 -10 B 20cos45 20sin45 C 7 cos30 -7sin30
6. 2. A cannon is placed at the bottom of a cliff 61.5 m high. If the cannon is fired straight upward, the cannonball just reaches the top of the cliff. (a) What is the initial speed of the cannonball? (b) Suppose a second cannon is placed at the top of the cliff. This cannon is fired horizontally, giving its cannonballs the same initial speed found in part (a). What is the range of this cannon ? (Assume the ground at the base of the cliff is level) a) v^2 = 2 g 61.5m b) calculate t from y = y_i - 1/2 g t^2 and subsitute t into x = v_0 t
7. 3. Two blocks, stacked one on top of the other, slide on a frictionless, horizontal surface (Figure). The surface between the two blocks is rough, however, with a coefficient of static friction equal to 0.47. (a) If a horizontal force F is applied to the 5.0-kg bottom block, what is the maximum value F can have before the 2.0-kg top block begins to slip? (b) If the mass of the top block is increased, does the maximum value of F increase, decrease, or stay the same? Explain!!!. a) F = f_s_max N .