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, Jacques pushes George's canoe with a force 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 but the final kinetic energy is zero.
B) The final momentum is in the direction opposite of but the final kinetic energy is zero.
C) The final momentum is in the direction of and the final kinetic energy is positive.
D) The final momentum is zero and the final kinetic energy is zero.
E) The final momentum is zero but the final kinetic energy is positive.

Question

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, Jacques pushes George's canoe with a force  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 but the final kinetic energy is zero. 
B) The final momentum is in the direction opposite of but the final kinetic energy is zero. 
C) The final momentum is in the direction of and the final kinetic energy is positive. 
D) The final momentum is zero and the final kinetic energy is zero. 
E) The final momentum is zero but the final kinetic energy is positive.

Quizplus · Accepted Answer

According to the conservation of momentum, the total momentum of the system before and after the push must be equal. Since Jacques pushed George's canoe in one direction, an equal and opposite momentum must be imparted to Jacques' canoe. Therefore, the final momentum is in the direction opposite of the force applied. However, since the canoes come to a complete stop, the final kinetic energy is zero.

Jacques and George Meet in the Middle of a Lake