Question

A coin is placed at the top of a two-story building, having a potential energy of 20 J. If it has a mass of 2.50 grams, what would be its velocity upon hitting the ground?

Answer 1

The velocity just before hitting the ground can be found from conservation of energy:

$$E=\dfrac12mv^2→v=\sqrt{2E/m}=126\text{ m/s}.$$