Energy is the ability to do work.

Work is a measure of the amount of energy changed from one form to another.

mechanical work is easily calculated using the above formula

Remember that Force = mass x acceleration.

If there is no acceleration there is no Force (unless there is another force acting in the opposite direction (e.g. gravity))

Work and Energy being measures of the same thing have the same units, the Joule, as named after James Joule

Types of Energy.

There are different types of energy and each have their own associated calculation et al.

In applied maths there are 2 many types of energy to consider.

Kinetic and Potential energy.

Kinetic is the energy a moving body has.

Potential energy is the energy a body has due to its position,

What is key to all this is that the total amount of energy in a system is constant

Lets look at the diagram below and see how the total sum of energy in the system remains the same from the start to the middle to the end.

For another explanation of the conservation of energy watch the following clip.


Power is the rate at which energy is converted

Power is measured in Watts, where 1 Watt is 1 Joule converted per second.

Convert the time into seconds to get an answer in Watts

so power = work / time

= F d / t ............. d/t = v

= F v


Like with Energy the amount of momentum in a closed system must also be conserved.

The total momentum before an interaction must


the total momentum after an interaction

Which is usually described mathematically as


u = velocity of body before interaction

v = velocity of body after interaction

m = mass

1 = first body

2 = 2nd body