Work-energy theorem: A constant horizontal pull acts on a sled on a horizontal frictionless ice pond. The sled starts from rest. When the pull acts over a distance x, the sled acquires a speed v and a kinetic energy K. If the same pull instead acts over twice this distance:

Question

Quizplus · Accepted Answer

The work-energy theorem states that the work done by the net force on an object is equal to the change in its kinetic energy. Since the pull is constant and horizontal, the net work done on the sled is simply the force multiplied by the distance traveled. Therefore, if the same pull is applied over twice the distance, the net work done is twice as much, and hence the change in kinetic energy is twice as much. Since the initial kinetic energy of the sled is zero, the final kinetic energy after the pull is applied is simply equal to the work done on the sled. Therefore, if the pull is applied over twice the distance, v remains the same but K doubles. Hence, the correct answer is C.

Work-Energy Theorem: a Constant Horizontal Pull Acts on a Sled