Item NG078002: After a rubber band is used to shoot a toy car across the floor, the total energy of the system will remain the same because the increase in the motion energy (kinetic energy) of the car is the same as the decrease in the elastic energy of the rubber band.

A student uses a rubber band to shoot a toy car across a level floor.  Imagine that no energy is transferred between the car and the floor or between the car and the air.

What happens to the total amount of energy in the system (car and rubber band) when the car is moving across the floor and is no longer in contact with the rubber band?

  1. The total amount of energy in the system will increase because the motion energy (kinetic energy) of the car increases and the elastic energy of the rubber band stays the same.
  2. The total amount of energy in the system will increase because the increase in the motion energy (kinetic energy) of the car is more than the decrease in the elastic energy of the rubber band.
  3. The total amount of energy in the system will decrease because the increase in the motion energy (kinetic energy) of the car is less than the decrease in the elastic energy of the rubber band.
  4. The total amount of energy in the system will remain the same because the increase in the motion energy (kinetic energy) of the car is the same as the decrease in the elastic energy of the rubber band.