Question

A 5.0kg ball is projected up along a plane that is inclined 20 degrees with the horizontal.What is its potential energy when it moved 23m up along the plane?

Answer 1

Potential energy depends on the position of an object. Therefore, all we need is to find how high the ball will be after 23 m of path:

$$h=d\text{ sin}20°=23\text{ sin}20°=7.87\text{ m}.$$

The energy is

$$E=mgh=5\cdot9.8\cdot7.9=390\text{ J}.$$