Physics

To find the kinetic energy of the object when it has fallen to a height of , we can use the principle of conservation of mechanical energy.

 

Initial total mechanical energy

At the initial height , the object has potential energy but no kinetic energy since it is at rest. The total mechanical energy at the start is just the potential energy:

 

Mechanical energy at the new height

When the object has fallen to a height of , its potential energy is:

 

By conservation of mechanical energy, the total mechanical energy remains constant, so the sum of the kinetic energy (KE) and potential energy (PE) at the new height must be equal to the initial mechanical energy: