Question

You do work on something when you lift if against gravity. Explain how work relates to gravitational potential energy using at least two complete content related sentences. If the lifted object is released, describe the change in energy. Be sure to define all terms used in both questions.

Answer 1

1) Work on something when you lift it against gravity

The work is the change in mechanical energy. Assuming the velocity is constant the kinetic energy does not change, and the change in mechanical energy is the change in potential energy.

Mathematically:

Work on the object = final potential energy - initial potential energy = m*g*H2 - m*g*H1 = m*g*ΔH.

2) Change in energy when the lifted object is released.

In this case, the object losses potential energy as it goes down and gains kynetic energy as the object gains speed. So, the energy is conserved along all the motion up to the object gets the ground, when all the energy is transformed into heat and sound.