Extra Credit

A 1.0-kg block and a 2.0-kg block are pressed together on a horizontal frictionless surface with a compressed very light spring between them. They are not attached to the spring. After they are released and have both moved free of the spring A) the heavier block will have more kinetic energy than the lighter block. B) both blocks will both have the same amount of kinetic energy. C) the lighter block will have more kinetic energy than the heavier block. D) both blocks will have equal speeds. E) the magnitude of the momentum of the heavier block will be greater than the magnitude of the momentum of the lighter block.

C) the lighter block will have more kinetic energy than the heavier block.

During a collision with a wall, the velocity of a 0.200-kg ball changes from 20.0 m/s toward the wall to 12.0 m/s away from the wall. If the time the ball was in contact with the wall was 60.0 ms, what was the magnitude of the average force applied to the ball? A) 26.7 N B) 13.3 N C) 107 N D) 16.7 N E) 40.0 N

C) 107 N

A shell explodes into two fragments, one fragment 25 times heavier than the other. If any gas from the explosion has negligible mass, then A) the momentum change of the lighter fragment is 25 times as great as the momentum change of the heavier fragment. B) the kinetic energy change of the lighter fragment is 25 times as great as the kinetic energy change of the heavier fragment. C) the momentum change of the lighter fragment is exactly the same as the momentum change of the heavier fragment. D) the momentum change of the heavier fragment is 25 times as great as the momentum change of the lighter fragment. E) the kinetic energy change of the heavier fragment is 25 times as great as the kinetic energy change of the lighter fragment.

C) the momentum change of the lighter fragment is exactly the same as the momentum change of the heavier fragment.

A billiard ball traveling at 3.00 m/s collides perfectly elastically with an identical billiard ball initially at rest on the level table. The initially moving billiard ball deflects 30.0° from its original direction. What is the speed of the initially stationary billiard ball after the collision? A) 2.59 m/s B) 0.750 m/s C) 2.00 m/s D) 0.866 m/s E) 1.50 m/s

E) 1.50 m/s 3sin(30)

A baseball is thrown vertically upward and feels no air resistance. As it is rising A) its momentum is not conserved, but its mechanical energy is conserved. B) its gravitational potential energy is not conserved, buts its momentum is conserved. C) both its momentum and its kinetic energy are conserved. D) both its momentum and its mechanical energy are conserved. E) its kinetic energy is conserved, but its momentum is not conserved.

A) its momentum is not conserved, but its mechanical energy is conserved.

In the figure, four point masses are placed as shown. The x and y coordinates of the center of mass are closest to A) (2.3 m, 2.6 m). B) (2.3 m, 2.8 m). C) (2.2 m, 2.7 m). D) (2.3 m, 2.7 m). E) (2.2 m, 2.6 m).

B) (2.3 m, 2.8 m).

A 310-g air track cart is traveling at 1.25 m/s and a 260-g cart traveling in the opposite direction at 1.33 m/s. What is the speed of the center of mass of the two carts? A) 2.80 m/s B) 0.0732 m/s C) 1.47 m/s D) 1.29 m/s E) 0.131 m/s

B) 0.0732 m/s vcm = [(310 g)(1.25 m/s) + (260 g)(-1.33 m/s)] / (310 + 260 g)

A 620-g object traveling at 2.1 m/s collides head-on with a 320-g object traveling in the opposite direction at 3.8 m/s. If the collision is perfectly elastic, what is the change in the kinetic energy of the 620-g object? A) It loses 0.47 J. B) It loses 0.23 J. C) It loses 1.4 J. D) It gains 0.69 J. E) It doesn't lose any kinetic energy because the collision is elastic.

B) It loses 0.23 J.

Jacques and George meet in the middle of a lake while paddling in their canoes. They come to a complete stop and talk for a while. When they are ready to leave, Jacquespushes George's canoe with a force F to separate the two canoes. What is correct to say about the final momentum and kinetic energy of the system if we can neglect any resistance due to the water? A) The final momentum is in the direction of F but the final kinetic energy is zero. B) The final momentum is in the direction of F and the final kinetic energy is positive. C) The final momentum is zero and the final kinetic energy is zero. D) The final momentum is zero but the final kinetic energy is positive. E) The final momentum is in the direction opposite of F but the final kinetic energy is zero.

E) The final momentum is in the direction opposite of F but the final kinetic energy is zero. *D) The final momentum is zero but the final kinetic energy is positive.

On a smooth horizontal floor, an object slides into a spring which is attached to another mass that is initially stationary. When the spring is most compressed, both objects are moving at the same speed. Ignoring friction, what is conserved during this interaction? A) momentum only B) momentum and potential energy C) kinetic energy only D) momentum and kinetic energy E) momentum and mechanical energy

E) momentum and mechanical energy