Physic Tutorials

# Mechanical Energy: Types And Examples

Energy is the ability to do work, and mechanical energy is one of the forms of energy. This form of energy is all around us. For example, a child on a swing is one of the familiar examples of the conservation of mechanical energy. So, in this article, I will discuss the types and uses of this form of energy.

## What is Mechanical Energy

There is a need to understand the meaning of mechanical energy before diving into the full details. Mechanical energy is either kinetic or potential energy; it can even mean the sum of potential and kinetic energy. So, to put it in simple terms, it is either energy in motion or energy stored in an object.

## Is Mechanical Energy Potential or Kinetic?

The answer is Yes. Mechanical energy can either be potential or kinetic energy. This is well spelt out when I defined mechanical energy.

Applying the law of conservation of energy to mechanical energy – it shows that the sum of potential energy and kinetic energy is always constant for a given body. Still, the energy may change from kinetic to potential or viz a viz. For example, when the pendulum swings from end to end, the system’s energy changes from potential to kinetic and vice-versa, but at each stage of the swing, the total energy remains constant.

## Types of Mechanical Energy

Mechanical energy is classified into two types – potential energy and kinetic energy.

Potential Energy

It is stored energy or the energy a body possesses by its position or state. Such stored energy is used to do work when the body is free to move. A heavy stone on top of a table has potential energy. when allowed to fall on a glass plate on the floor, it will shatter the plate. The stone’s potential energy due to its position above the floor, is expended in shattering the plate.

A body may have potential energy due to its position in a force field. If the force field is the gravitational field, the body is said to possess gravitational potential energy. the stone resting on top of a table has gravitational potential energy due to its height above the ground level. If the body is of mass m and the height of the table is h, then the gravitational potential energy is given by

Ep = mgh

Kinetic Energy

It is the energy possessed by a body by its position. While gravitational potential energy depends on the body’s mass, its height above a reference level and the acceleration due to gravity, kinetic energy depends only on the body’s mass and velocity. The kinetic energy of a body in motion is given by

K.E = ½ mv2

## Examples of Mechanical Energy

The examples of kinetic and potential energy are also the same as mechanical energy.

Potential energy

• A magnet at rest in a magnetic field
• An electric charge at rest in an electric field
• A coiled spring when stretched or compressed
• Chemical potential energy is released when petrol, wood, and other fuel sources burn

Kinetic energy

• A student running a race
• An object falling freely under gravity
• Wind or air in motion
• Electrical charges in motion