CIE AS Physics (9702) exams from 2022

Revision Notes

5.1.5 Derivation of P = Fv

Derivation of P = Fv

  • Moving power is defined by the equation:

 

Moving power equation, downloadable AS & A Level Physics revision notes

 

  • This equation is only relevant where a constant force moves a body at constant velocity. Power is required in order to produce an acceleration
  • The force must be applied in the same direction as the velocity

 

Derivation

  • The derivation for this equation is shown below:

 

Derivation of moving power, downloadable AS & A Level Physics revision notes

Derivation of P = F × v

 

Worked example

Worked example - P = fv (1), downloadable AS & A Level Physics revision notes
Worked example - P = fv (2), downloadable AS & A Level Physics revision notes

Exam Tip

The force represented in exam questions will often be a drag force. Whilst this is in the opposite direction to its velocity, remember the force needed to calculate the power is equal to (or above) this drag force to overcome it therefore you equate it to that value.

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