Two balls of equal size are dropped from the same height from the roof of a building. One ball has twice the mass of the other. When the balls reach the ground, how do the kinetic energies of the two balls compare?
A)The lighter one has one fourth as much kinetic energy as the other does.
B)The lighter one has one half as much kinetic energy as the other does.
C)The lighter one has the same kinetic energy as the other does.
D)The lighter one has twice as much kinetic energy as the other does.
E)The lighter one has four times as much kinetic energy as the other does.

Question

Quizplus · Accepted Answer

Since both balls are dropped from the same height, they have the same potential energy at the start. When the balls reach the ground, they both have the same amount of kinetic energy, which is equal to the initial potential energy. However, since one ball has twice the mass of the other, the kinetic energy is distributed over twice the mass, resulting in a lower velocity. The kinetic energy of the lighter ball is therefore half that of the heavier ball. Hence, the lighter one has one half as much kinetic energy as the other does.

Two Balls of Equal Size Are Dropped from the Same