AP Physics B Chapter 9 Practice Test Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A 2.00-g bullet hits and becomes embedded in a 5.00-kg wood block which is hanging from a 1.20-m long string. This causes the block to swing through an arc of 3.50°. What was the speed of the bullet before it hit the block? A) 25.3 m/s B) 262 m/s C) 524 m/s D) 789 m/s E) 16.7 m/s
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2) Two ice skaters, one with a mass of 45 kg and the other with a mass of 60 kg, push off against one another starting from a stationary position. After they have pushed off, the relative speed at which they separate is 0.600 m/s. What is the speed of the 60-kg skater? A) 0.343 m/s B) 0.750 m/s C) 0.257 m/s D) 0.375 m/s E) 0.225 m/s
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3) A 900-kg car traveling 30.0° south of east at 12.0 m/s collides with a 750-kg car traveling north at 17.0 m/s. The cars stick together. What is the speed of the wreckage just after the collision? A) 12.2 m/s B) 7.21 m/s C) 20.4 m/s D) 25.0 m/s E) 17.3 m/s
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4) A 0.330-kg volleyball is thrown vertically downward with a speed of 0.150 m/s. It takes it 0.0655 s to reach the ground. What is the magnitude of its momentum just before it hits the ground? A) 0.212 kg·m/s B) 0.0216 kg·m/s C) 0.163 kg·m/s D) 0.262 kg·m/s E) 0.0418 kg·m/s
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5) A curling stone slides on ice with a speed of 1.70 m/s and collides elastically with an identical, stationary curling stone. After the collision, the first stone has a velocity of 0.800 m/s in a direction that makes a counterclockwise angle of 61.9° with its original direction of travel. At what speed and what direction is the second stone traveling after the collision? A) 1.60 m/s at a clockwise angle of 34.2° B) 1.40 m/s at a clockwise angle of 32.3° C) 1.40 m/s at a clockwise angle of 19.1° D) 1.60 m/s at a clockwise angle of 28.1° E) 1.50 m/s at a clockwise angle of 28.1°
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6) A ping-pong ball originally at rest is hit head-on by a bowling ball moving with initial speed v 0 . It is given that the mass of the ping-pong ball is as good as negligible in comparison with the mass of the bowling ball. What is the speed of the ping-pong ball after this elastic collision? v0 A) v0 B) C) 2v 0 D) 4v 0 E) 8v 0 2
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7) A freight car moves along a frictionless level railroad track at constant speed. The freight car is open on top. A large load of coal is suddenly dumped into the car. What happens to the speed of the freight car? A) It remains the same. B) It increases. C) It becomes zero. D) It decreases. E) Cannot be determined from the information given.
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8) A curling stone slides on ice with a speed of 2.0 m/s and collides inelastically with an identical, stationary curling stone. After the collision, the first stone is deflected by a counterclockwise angle of 28° from its original direction of travel, and the second stone moves in a direction that makes a 42° clockwise angle with the original direction of travel of the first stone. What fraction of the initial energy is lost in this collision? A) 0.12 B) 0.36 C) 0.24 D) 0.64 E) 0.48
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9) A 0.140-kg baseball is dropped and reaches a speed of 1.20 m/s just before it hits the ground. It rebounds with a speed of 1.00 m/s. What is the change of the ball's momentum? A) 0.0280 kg·m/s upwards B) 0.308 kg·m/s downwards C) 0.0280 kg·m/s downwards D) 0 kg·m/s E) 0.308 kg·m/s upwards
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10) A rocket is fired in a gravity-free environment in deep space. The rocket has an initial mass of 8000 kg and ejects gas with a velocity of 2000 m/s. How much gas must be ejected in the first second to give the rocket an acceleration of 30.0 m/s2 ?
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11) A 340-g air track cart traveling at 1.25 m/s collides elastically with a 300-g cart traveling in the opposite direction at 1.33 m/s. What is the speed of the 300-g cart after the collision? A) 0.475 m/s B) 2.80 m/s C) 0.899 m/s D) 1.41 m/s E) 0.0693 m/s
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12) A batter hits a 0.140-kg baseball that was approaching him at 40.0 m/s and, as a result, the ball leaves the bat at 30.0 m/s in the direction of the pitcher. What is the magnitude of the impulse delivered to the baseball? A) 1.40 Ns B) 9.80 Ns C) 5.60 Ns D) 4.90 Ns E) 7.00 Ns
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13) In a collision between two unequal masses, how does the impulse imparted to the smaller mass by the larger mass compare with the impulse imparted to the larger mass by the smaller one? A) It is smaller. B) They are equal. C) It is larger. D) The answer depends on the ratio of the masses. E) The answer depends on how fast they are moving.
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14) A 60.0-kg man stands at one end of a 20.0-kg uniform 10.0-m long board. How far from the man is the center of mass of the man-board system? A) 9.00 m B) 1.25 m C) 7.50 m D) 5.00 m E) 2.50 m
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A) 15.0 kg
B) 12.0 kg
C) 150 kg
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D) 120 kg
E) 7.50 kg
15) An assault rifle fires an eight-shot burst in 0.40 s. Each bullet has a mass of 7.5 g and a speed of 300 m/s as it leaves the gun. What is the average recoil force on the gun during that burst? A) 16 N B) 5.6 N C) 45 N D) 23 N E) 2.0 N
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16) A 0.140-kg baseball is dropped from rest from a height of 2.2 m above the ground. It rebounds to a height of 1.6 m. What change in the ball's momentum occurs when the ball hits the ground? A) 0.350 kg·m/s upwards B) 0.117 kg·m/s upwards C) 0.117 kg·m/s downwards D) 1.70 kg·m/s upwards E) 0.350 kg·m/s downwards
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17) Three masses are located in the x-y plane as follows: a mass of 6 kg is located at (0 m, 0 m), a mass of 4 kg is located at (3 m, 0 m), and a mass of 2 kg is located at (0 m, 3 m). Where is the center of mass of the system? A) (1 m, 0.5 m) B) (2 m, 1 m) C) (1 m, 2 m) D) (1 m, 1 m) E) (0.5 m, 1 m)
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18) A puck with a mass m1 = 28.0 g moving at 1.00 m/s approaches a stationary puck with a mass m2 = 102 g on an air table and they undergo a two-dimensional elastic collision. As a result of their interaction, the incident puck moves away with a speed v 1 = 0.785 m/s and the other puck moves
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19) In a physics demonstration, two rubber balls are dropped down a tube towards the ground, with the lighter ball behind, and not quite in contact with, the heavier ball. The heavier ball collides with the ground and bounces, then collides with the still descending lighter ball. Assume that all the collisions are elastic. In one such demonstration, the heavier ball has a mass of 500 grams, the lighter one a mass of 100 grams, and they are released 1.00 m above the ground. How high does the lighter ball rise after the two collisions? A) 1.00 m B) 5.44 m C) 2.95 m D) 10.3 m E) 5.89 m
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20) A tennis ball undergoes an elastic collision when it hits the ground and bounces up. It is given that the speed of the ball just before it hits the ground is -v0 and immediately after rebounding it is +
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away with a speed v 2 in a different direction. What is the angle between the velocities v1 and v2? A) 165° B) 45.0° C) 123° D) 90.0° E) 85.0°
v0 . Which of the statements below is true?
A) The momentum of the ball does not change but the momentum of Earth changes. B) The momentum of the ball changes but the momentum of Earth does not. C) The momentum of the ball changes and the momentum of Earth also changes by the same amount. D) Neither the momentum of the ball nor the momentum of Earth changes. E) Additional information is needed to answer this question.
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 21) An air track cart with mass m and speed v moving along an air track collides with a stationary cart with a mass m/3. After the collision the first cart has a speed v/2. What is the speed of the second cart? 3
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22) When a gun is fired, which has the greater kinetic energy: the bullet or the recoiling gun?
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23) An 80. kg man is skating Northward and happens to collide with a 20. kg boy who is ice skating toward the East. Immediately after the collision, the man and boy are seen to be moving together at 2.5 m/s in a direction 60 degrees North of East. How fast was the boy moving before the collision?
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24) A 900-kg car traveling east at 15.0 m/s collides with a 750-kg car traveling north at 20.0 m/s. The cars stick together. (a) What is the speed of the wreckage just after the collision? (b) In what direction does the wreckage move just after the collision?
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25) Three masses are positioned at the following coordinates: 3.0 kg at (3,2); 4.0 kg at (0,-1); and 5.0 kg at (5,-7). What are the coordinates of the center of mass of the system?
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TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false. 26) When objects stick together after colliding, the collision is completely elastic.
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27) Internal forces cannot change the total kinetic energy of a system.
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28) A particle that has zero momentum must also have zero kinetic energy.
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29) A system that has zero momentum must also have zero kinetic energy.
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30) In a one-dimensional elastic collision of two identical masses, the masses exchange velocities.
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