MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A ball can be rolled down one of four different ramps, as shown below. The final elevation loss of each of the ramps is the same. Neglecting friction, for which ramp will the speed of the ball be the highest at the bottom? 1) A) The speed of the ball will be the same for all ramps. B) Ramp X C) Ramp Y D) Ramp Z 2) A block slides down a frictionless inclined ramp. If the ramp angle is 17.0 and the length of it is 30.0 m, find the speed of the block as it reaches the end of the ramp, assuming it started sliding from rest at the top. A) 13.1 m/s B) 172 m/s C) 9.26 m/s D) 24.0 m/s 2) 3) A 1000.0 kg car experiences a net force of 9500 N while decelerating from 30.0 m/s to 23.4 m/s. How far does it travel while slowing down? A) 20 m B) 22 m C) 19m D) 17 m 3) 4) A 10.0 kg block on a table is connected by a string to a 63 kg mass, which is hanging over the edge of the table. Assuming that frictional forces may be neglected, what is the magnitude of acceleration of the 10.0 kg block when the other block is released? (See the figure.) 4) A) 7.5 m/s2 B) 9.0 m/s2 C) 8.1 m/s2 D) 8.5 m/s2 5) A massless spring hangs from the ceiling. How much does its potential energy increase, if a 28.8-kg mass is attached to it? The spring constant is 4800 N/m. A) 8.3 J B) 17 kj C) 8.3 kj D) 17 J 5) 6) Joe and Bill throw identical balls vertically upward. Joe throws his ball with an initial speed of twice as high as Billʹs ball. The maximum height of Joeʹs ball will be A) eight times that of Billʹs ball. B) roughly 1.3 times that of Billʹs ball. C) four times that of Billʹs ball. D) two times that of Billʹs ball. E) equal to that of Billʹs ball. 6) 1
7) Two cyclists, who weigh the same and have identical bicycles, ride up the same mountain, both starting at the same time. Joe rides straight up the mountain, and Bob rides up the longer road that has a lower grade. Joe gets to the top before Bob. Which statement is true? A) Ignoring friction and wind resistance, the average power exerted by Bob and Joe was the same, but Joe exerted more work in getting there. B) Ignoring friction and wind resistance, the amount of work done by Joe is greater than the amount of work done by Bob, and the average power exerted by Joe is greater than that of Bob. C) Ignoring friction and wind resistance, Bob and Joe exerted the same amount of work, and the average power of each cyclist was also the same. D) Ignoring friction and wind resistance, the amount of work done by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greater than that of Bob. 7) 8) Calculate the impulse associated with a force of 4.5 N that lasts for 1.4 s. A) 6.3 kg m/s B) 6.9 kg m/s C) 5.7 kg m/s D) 5.0 kg m/s 8) 9) You are standing on a skateboard, initially at rest. A friend throws a very heavy ball toward you. You can either catch the object or deflect the object back toward your friend (such that it moves away from you with the same speed as it was originally thrown). What should you do in order to maximize your speed on the skateboard? A) deflect the ball back B) catch the ball C) Your final speed on the skateboard will be the same regardless whether you catch the ball or deflect the ball. 9) 10) A block starts from rest at the top of a 31.0 inclined plane and encounters a spring, of constant 3.4 kn/m, rigidly attached to the plane. If the blockʹs mass is 33.0 kg and it compresses the spring by 37.0 cm, find the distance the block travelled before it encountered the spring. A) 137 cm B) 1.0 m C) 74m D) 82.6 cm 10) 11) A block is at rest on a rough incline as shown. 11) The frictional force acting on the block, along the incline, is A) equal to the weight of the block. B) zero. C) less than the weight of the block. D) greater than the weight of the block. 12) A child pulls on a wagon with a force of 75 N. If the wagon moves a total of 42 m in 3 min, what is the average power generated by the child, in watts? A) 22 W B) 18 W C) 24W D) 27 W 12) 2
13) In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after are given. The collision is: A) partially inelastic. B) perfectly elastic. C) completely inelastic. D) characterized by an increase in kinetic energy. E) not possible because momentum is not conserved. 13) 14) Calculate the kinetic energy of a 0.300 kg baseball thrown at a velocity of 44 m/s. A) 290 J B) 510 J C) 580 J D) 440 J 14) 15) Two unequal masses M and m are connected by a light cord passing over a pulley of negligible mass. When released, the system accelerates. Friction is negligible. 15) Which figure below gives the correct free-body force diagrams for the two masses in the moving system? A) B) 3
C) D) 16) A person stands on the edge of a cliff. She throws three identical rocks with the same speed. Rock X is thrown vertically upward, rock Y is thrown horizontally, and rock Z is thrown vertically downward. Assuming the elevation loss of the three rocks is the same (the base of the cliff is flat), which rock hits the ground with the highest speed? A) They all hit the ground with the same speed. B) Rock X C) Rock Y D) Rock Z 16) 17) A spring stretches by 21.0 cm when a 135 N object is attached. What is the weight of a fish that would stretch the spring by 44.9 cm? A) 63 N B) 289 N C) 405 N D) 176 N 17) 18) An object attached to a spring is pulled across a frictionless surface. If the spring constant is 45 N/m and the spring is stretched by 0.88 m when the object is accelerating at 1.4 m/s2, what is the mass of the object? A) 36 kg B) 24 kg C) 31 kg D) 28 kg 18) 19) A container explodes and breaks into three fragments that fly off 120 apart from each other, with mass ratios 1:4:2. If the first piece flies off with a speed of 6.0 m/s, what is the speed of the other two fragments? (All fragments are in the plane.) A) 1.5 and 0.9 m/s B) 1.5 and 3.0 m/s C) 1.0 and 3.0 m/s D) 0.9 and 3.0 m/s 19) 20) Two friends are standing on opposite ends of a canoe. The canoe is initially at rest with respect to the lake. The person on the right throws a very massive ball to the left, and the person on the left catches it. After the ball is caught (ignoring friction between the canoe and the water), the canoe is A) moving to the right. B) moving to the left. C) stationary. 20) 21) A 1200 kg car moving at 15.6 m/s collides with a stationary car of mass 1500 kg. If the two vehicles lock together, what is their combined velocity immediately after the collision? A) 5.5 m/s B) 8.6 m/s C) 6.9 m/s D) 12.1 m/s 21) 4
22) An 8 g bullet is shot into a 4.0 kg block, at rest on a frictionless horizontal surface. The bullet remains lodged in the block. The block moves into a spring and compresses it by 3.7 cm. The force constant of the spring is 2500 N/m. In the figure, the initial velocity of the bullet is closest to: A) 460 m/s B) 440 m/s C) 480 m/s D) 520 m/s E) 500 m/s 22) 23) A child does 350 J of work while pulling a box from the ground up to his tree house with a rope. The tree house is 8.4 m above the ground. What is the mass of the box? A) 2.6 kg B) 4.3 kg C) 3.9 kg D) 3.2 kg 23) 24) Two pendulums of equal length l = 0.45 m are suspended from the same point. The pendulum bobs are steel spheres. The first bob is drawn back to make a 35 angle with the vertical. If the first bob has mass 0.25 kg and the second has mass 0.85 kg, how high will the second bob rise above its initial position when struck elastically by the first bob after it is released? A) 1.4 cm B) 1.7 cm C) 2.3 cm D) 2.0 cm 24) SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 25) Describe the energy transfers that take place as you use a slingshot to shoot a rock into the air, it rises to a peak, then falls, and finally hits the ground and stops without bouncing. 25) 26) A cannon recoils after it fires a shell. If you measure the range of the shell, can you find the energy released by the gunpowder? 26) 27) A rubber ball is dropped from a height h above the ground. Describe the motion of the ball for many bounces if the collision is completely elastic. 27) 5
Answer Key Testname: 201_SUMMER2009_2_V2 1) A 2) A 3) C 4) D 5) A 6) C 7) D 8) A 9) A 10) B 11) C 12) B 13) C 14) A 15) B 16) A 17) B 18) D 19) B 20) C 21) C 22) A 23) B 24) B 25) Chemical energy in your muscles is transformed into elastic potential energy as you stretch the slingshot; the elastic potential energy changes to kinetic energy of the rock as the sling is released; the rock s kinetic energy gradually changes to gravitational potential energy as it rises and stops at its peak; the gravitational potential energy is transformed back into kinetic energy as the rock falls; the rock s kinetic energy changes to heat in the ground and the rock itself, once the rock hits the ground and stops. 26) No. During the same time it takes the shell to clear the barrel of the cannon, there are frictional forces acting on it. These are external to the components of the explosion. 27) If the collision is completely elastic, the ball will continue to bounce to the same height h after every bounce, forever. It should be noted that this is not completely realistic, which implies that the collisions are not 100% elastic in real life. 6