The rate of doing work is called power.The basic difference between average and instantaneous power is that average power is the ratio of total work and total time. While instantaneous power is the limiting value of average power.
From the statement of work it is not clear that same amount of work done in one second or in 1 hour.The rate at which work done is often interest in practical applications.
Power formula physics
Average power formula
The ratio of total work to the total time is called average power.Mathematically it is expressed as
If “ΔW” is the work done in time “Δt” then average power will be:
Instantaneous power formula
The limiting value of average power such that Δt approaches to zero is known as instantaneous power.
If “Δt” approaches to zero then power will be instantaneous and given by:
ΔW is the work done in short interval of time Δt is following the instant t.
si unit of power
In international system of units the si unit of power is watt.
Watt definition physics
Watt is defined as:”When a body does work of one joule in one second is called its one watt power.”
1 watt = 1J/1S
The multiples of power are KW,MW ,GW ….
In British engineering system the unit of power is horse power “hp”.
Definition of horse power
When a body does work 550 ft-1b in one second is called its one horse power.
Dimensions of power
The dimensions of power are:
Relation between power and force
This is the required relation between power and force.