Question

A child swings on a swing at the playground. The motion of the swing resembles the motion of a pendulum. When is the kinetic energy of the swing zero?

1) When it is moving the fastest
2) It is never zero
3) When it stops moving at the top of the swing
4) At the bottom of the swing

Answer 1

The kinetic energy of a swing, much like a pendulum, is zero at the top of its path where all its energy is potential. It increases as the swing descends and decreases as the swing rises again until it momentarily stops at the highest point.

Step-by-step explanation:

The motion of a swing closely resembles that of a pendulum in terms of the energy transformations that occur. The kinetic energy of the swing is zero when the swing is at the top of its path because at this point all of the energy is in the form of potential energy. As the swing descends, kinetic energy increases because it is converting potential energy into kinetic energy. At the bottom of the swing, the kinetic energy is at its maximum because potential energy has been fully converted into kinetic energy. On the upward arc, kinetic energy is converted back into potential energy until it comes to a temporary stop at the top of the swing. Therefore, the correct answer is 3) When it stops moving at the top of the swing.