Efficiency
Efficiency: how much useful energy something makes.
Efficiency = useful energy output/ total energy input
Efficiency is measured as a percentage
Example
Power
Power: the amount of work that can be done in a period of time. The faster work is done the greater the power
Power is measured in watts (joules per second)
Power = work done/ time taken
Example:
1000j of work is done in 2 seconds the power is calculated like this
1000/2 = 500 watts
Useful work = force x speed