power

Power

What is power?

• Power is developed as an engine or machine does work

• Power is the rate of doing work, usually by the driving force of an engine

  • It is the same as work done per second

  • The work done is converting fuel (a type of chemical energy) into a driving force

• Power is a scalar quantity and can only take a positive value

How is power calculated?

• Power is the rate of doing work and can be calculated by the formula

Where WD is the work done by the driving force in Joules and t is the time in seconds

• If a driving force, F N, is acting on an object moving with velocity, v m s^-1 then power can be calculated using the formula

• • The velocity must be in the same direction as the force

  • When labelling forces on a diagram, the rearrangement  can be useful to write the force generated by a particular power, at a particular speed

  • For a constant velocity and a constant force, the above formula can be derived by recalling the formula

where is speed or velocity and  is distance or displacement.

• The derivation can also be shown for a constant force, F N and considering the rate of doing work over a very small interval of time

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