Question

A 25-centavo coin is dropped from the top of a 5.0-m high building. 20.0 seconds later, a 10-peso coin is dropped from the same point where the first coin was dropped. After how many seconds will it take the 10-peso coin to hit the ground?

Answer 1

Start a thought experiment:

1) We hold the 10-peso coin in left hand and stopwatch in right hand

2) We drop the 10-peso coin and immediately start the stopwatch

3) We stop the stopwatch as the coin reaches the ground. After how many seconds as we dropped it?

4) After approximately

$$t=\sqrt{2h/g}=\sqrt{2·5/9.8}=1.01\text{ s}$$

the 10-peso coin will hit the ground.