Work, energy and power
Theme: YOU AND ENERGY
Basic science J.S.S.2 Second Term
WEEK 2
Work, energy and power
Performance Objectives
The student should be able to:
- Explain the meaning of work, energy and power
Content
Work energy and power
Work
Work is said to be done when a force applied to an object moves that object.
We can define work as an activity involving a movement and force in the direction of the force. For example, a force of 30 newtons (N) pushing an object 3 meters in the same direction of the force will do 90 joules (J) of work.
When we kick a football, we are exerting an external force called F, and due to this force (kick), the ball moves to a certain distance. This disposition of ball from position A to B is known as displacement (d). This work is said to be done and can be calculated as W = F × d
Work done = force × distance = F × d
Joules is the unit of Work.
Energy
Energy is the ability to perform work. Energy can neither be created nor destroyed. It can only be transformed from one kind to another. The unit of energy is the same as of Work i.e. Joules. Energy is found in many things and thus there are different types of energy.
All forms of energy are either kinetic or potential. The energy in motion is known as Kinetic Energy whereas Potential Energy is the energy stored in an object and is measured by the amount of work done.
Types of energy
Some other forms of energy are given below:
- Mechanical energy
- Mechanical wave energy
- Chemical energy
- Electric energy
- Magnetic energy
- Radiant energy
- Nuclear energy
- Ionization energy
- Elastic energy
- Gravitational energy
- Thermal energy
- Heat Energy
Unit of energy
The SI unit of energy is joules (J), which is named in honour of James Prescott Joule.
Power
Power can be defined as the rate at which work is done i.e. energy converted.
It is the amount of energy consumed per unit time.
As discussed power is the rate of doing work. Therefore it can be calculated by dividing work done by time. The formula for power is given below.
P = W/t
Where
P = Power
W = work done
T = time taken
The SI unit of power in Watts