Mechanical Energy Stores

Mechanical Energy is a form of energy associated with the movement and position of an object.
It can be separated into two sub-categories: Kinetic Energy and Potential Energy.

Kinetic Energy

Kinetic Energy is the energy of an object due to its motion. It depends on both, the mass and the speed of the object.
It can be calculated using the following equation: Kinetic Energy = 0.5 x mass x velocity².
Whenever an object’s speed (or velocity) changes, there is an associated change in the object’s kinetic energy.

Potential Energy is the energy stored in an object due to its position in a force field, typically a gravitational field.
In the case of gravitational potential energy, it depends on the height of the object above the Earth’s surface, the mass of the object, and the acceleration due to gravity.
It can be calculated using the following equation: Potential Energy = mass x gravity x height.
When an object’s height or position changes in a gravitational field, there is an associated change in its gravitational potential energy.

In a closed system (one not affected by external forces), the total mechanical energy remains constant. This principle is known as the Conservation of Mechanical Energy.
In other words, when a system is conserved, the sum of kinetic energy and potential energy is constant: kinetic energy may transfer to potential energy and vice versa, but their sum remains constant.
This principle is often seen in simple pendulum and roller coaster systems, where kinetic energy (highest at bottom of swing or descent) continually converts to gravitational potential energy (highest at top of swing or ascent) and back.

Any change in these energy stores is due to work done, which can be done by a force like gravity, or a mechanical force.
Work done is defined as force multiplied by distance, in the direction of the force. It is measured in joules. Likewise, any work done on a system increases its energy.