Air drag is a resistive force that acts on objects moving through air.

In an isolated system, the total mechanical energy is conserved:

$$E_{\text{total}} = E_k + E_p = \text{constant}$$

Elastic potential energy is the energy stored in an elastic object, such as a spring, when it is compressed or stretched.

Friction is a force that opposes the motion of an object.

Gravitational potential energy is the energy stored due to the position of an object in a gravitational field.

Mechanical energy is the sum of an object's kinetic energy and potential energy.

Potential energy is the energy stored in an object due to its position or configuration.