A 20 N ball and a 40 N ball are dropped at the same time from a height of 10 meters. Air resistance is negligible. Which of the following statements is accurate?
A) After 1 second has elapsed, both balls have the same kinetic energy, since they have the same acceleration.
B) The heavy ball has a greater acceleration and falls faster.
C) Both balls hit the ground at the same time but gravity does more work on the heavy ball than on the light ball.
D) The light ball has a greater speed, since it can accelerate faster than the heavy ball.

Question

Quizplus · Accepted Answer

Both balls have the same acceleration due to gravity, so A is incorrect. The heavy ball has a greater force acting on it due to its greater weight, but this does not necessarily mean it has a greater acceleration or falls faster, so B and D are incorrect. Both balls are dropped from the same height and experience the same change in potential energy, so they have the same amount of work done on them by gravity. However, since the heavy ball has a greater weight, it experiences a greater force and therefore a greater amount of work is done on it by gravity, so C is accurate – gravity does more work on the heavy ball than on the light ball. Both balls hit the ground at the same time because they have the same acceleration due to gravity.

A 20 N Ball and a 40 N Ball Are