Item NG065004: A pendulum stops swinging because the motion energy of the ball is transferred somewhere else, like the air, as the ball swings from side to side.

A student is playing with a pendulum (a ball attached to the end of a string).  He gives the ball a push and watches the ball as it swings from side to side.  After a while, the ball stops swinging.

Why does the ball stop swinging?

  1. The motion energy (kinetic energy) of the ball is transferred somewhere else, like the air, as the ball swings from side to side.
  2. A little bit of the ball’s motion energy (kinetic energy) is used up each time it swings from side to side, but the motion energy is not transferred anywhere else.
  3. Some motion energy (kinetic energy) is transferred somewhere else, like the air, and some motion energy is used up.
  4. An object only has motion energy (kinetic energy) when a person makes it move, and the student is no longer pushing the ball.