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