Question

A man weighing120𝑙𝑏𝑠, climb up a stairway inclined 45° consisting of 20 𝑠𝑡𝑒𝑝𝑠 each step 6" high. What is his potential energy at the top?

Answer 1

The height of the man at the very top:

$$H=20·6\cos45°=84.9",$$

equivalent to 2.16 m. The weight of 120 lbs is equivalent to 54.4 kg. Therefore, the energy is

$$E=mgH=1152\text{ J}.$$