if you drop a tennice ball and a boling ball from a 20ft building, assuming there is no air resistance, will they fall at the same time, or will one fall first

Yes, they will fall at the same time. This is due to the principle of equivalence, a key concept in Einstein's theory of general relativity. It states that the force of gravity experienced by a body is independent of its mass. So, assuming there is no air resistance, a tennis ball and a bowling ball dropped from the same height will hit the ground at the same time. Here are the steps:

1. Both balls are dropped from a 20ft building. The only force acting on them is gravity.
2. Gravity accelerates all objects at the same rate, regardless of their mass. This rate is approximately 9.8 m/s² on Earth.
3. Without air resistance to slow down either ball, they both continue to accelerate at this rate.
4. Since they start from rest, are subject to the same acceleration, and cover the same distance, they must take the same amount of time to reach the ground.

So, in a vacuum where there is no air resistance, a tennis ball and a bowling ball dropped from the same height will fall at the same rate and hit the ground at the same time.