Final answer:
Dropping a tennis ball and a basketball together side by side results in them hitting the ground at the same time due to gravity. When a tennis ball is dropped on top of a basketball, it bounces higher because the basketball transfers some of its momentum to the tennis ball. The reverse situation, with a basketball on top, would see the basketball bounce up with slightly less energy, affecting the tennis ball differently.
Step-by-step explanation:
When you hold a tennis ball side by side and in contact with a basketball and drop them together, both balls hit the ground at approximately the same time due to gravity acting on them equally. The main force at work here is gravity, and it accelerates all objects at the same rate regardless of their mass when air resistance is negligible. Now, if you hold the tennis ball above the basketball and drop them, you might observe that the tennis ball bounces higher than expected. This occurs because the basketball hits the ground first, transfers some of its upward momentum to the tennis ball, and propels it higher than it would have gone if dropped alone.
If you reverse the situation and place the basketball above the tennis ball, upon dropping them, the basketball would hit the ground and bounce back up, potentially with slightly less energy than if it were dropped alone due to energy transfer during the collision with the tennis ball. The tennis ball may be propelled to the side or absorb some impact and not bounce as high due to the larger mass of the basketball directly above it, affecting the collision outcome.