Item RG082002: Kinetic energy is proportional to the speed squared, so when a moving object has its speed decreased by half the kinetic energy of that object decreased by one fourth.

A child rolls a bowling ball down a flat lane toward a set of pins at a bowling alley. As the bowling ball rolls, it slows down.

When the bowling ball is traveling at half the initial speed, what will the kinetic energy (motion energy) of the bowling ball be?

  1. The kinetic energy of the bowling ball will be half of what it was because the amount of kinetic energy an object has is directly proportional to its speed.
  2. The kinetic energy of the bowling ball will be one fourth of what it was because the amount of kinetic energy an object has is directly proportional to the square of its speed.
  3. The kinetic energy of the bowling ball will be double what it was because the amount of kinetic energy an object has is inversely proportional to its speed.
  4. Even though the speed of the bowling ball is half of what it was, the kinetic energy of the bowling ball will stay the same because the amount of kinetic energy an object has is not related to the speed of a moving object.