Wave
via ScienceTm

In previous lessens we looked at what is a wave. If you’re unclear on this topic click here to read more about waves.
In physics there are two known types of waves, these are:

1. Mechanical Wave
2. Electromagnetic wave

The differences between these two lie in their means of transferring energy. One may not see the difference between sound waves and light rays because as humans we aren’t capable of seeing such things with our naked eyes but thanks to human intelligence and through many research scientists were able to detect movement of energy in waves and thus differentiate the means by which they are transferred.

What are Mechanical Waves?
Mechanical waves are those that need a material medium with particles to enable them to move. Therefore these waves can’t “travel on their own”.

Examples of mechanical waves:

• Sound Waves
• Water Waves
• Waves in springs

What is Electromagnetic wave?
Electromagnetic waves are those that do not need any material medium to enable them to move. Therefore these waves can travel on their own. These waves can travel through a vacuum.

Examples of electromagnetic waves:

• Visible light
• X-rays
• Infrared rays
• Ultraviolet rays
• Radio waves

What is Energy?
Energy can be defined as the capacity to do work.

Types of Energy


Mechanical Energy: - By definition mechanical energy is the sum of Kinetic energy(K.E) and Potential energy(P.E).

Mechanical energy = Kinetic Energy + Potential Energy

Kinetic Energy: - Kinetic energy is the energy due to a body’s motion.

K.E = 1/2 mass × velocity²

Potential Energy: - Potential Energy is energy due to a body’s position or condition.

P.E = mass × gravity × height

Law of Conservation of mechanical energy
In a system where only forces associated with potential energy are acting (gravitational/ elastic), the sum of the Kinetic and Potential energies is constant.

K.E + P.E = Constant

These conditions exist for any object rising of falling above the earth’s surface:

1. For a body that is rising:

Loss in K.E = Gain in P.E

     2.  For a body falling towards the earth:

Loss in P.E = Gain in K.E

What is momentum?
Momentum can be defined as the product of mass and velocity (m x v).

Principle of conservation of momentum:

The principle of conservation of momentum states that the total linear momentum of a system of interacting (colliding) bodies, on which no external force is acting remains constant.

This principle is basically saying momentum before collision is equal to momentum after collision.

Types of collisions:

There are two types of collisions covered in physics they are Elastic and Inelastic collisions.

Elastic collisions are those formed when the colliding bodies separate after collision, hence its name. When elastic collisions take place two things are conserved, Momentum and Kinetic Energy (K.E.), meaning none is lost from the system.

Therefore in elastic collisions momentum before collision is equal to momentum after collision, and similarly Kinetic energy before collision is equal to kinetic energy after collision.

In-elastic collisions refer to collisions in which the objects remain or stick together after collision. Seeing that the objects remain together after collision Kinetic energy is therefore not conserved only momentum is conserved.