Power

  2. Mechanics
  3. Work and energy
  4. Power
    5. 15'

Power is defined as the rate at which work is done:

\(P={W\over t}\)

 Watt is the unit of power?

Just kidding... the unit of power is the Watt (W), equivalent to J s-1.

 kWh is a unit of energy and kW per hour isn´t anything

Key Concepts

Power when kinetic energy gained

A powerful car has a high acceleration; it is able to change kinetic energy in a short time.

 

Power when gravitational potential energy gained

A powerful truck can do a lot of work in a short time, so can move a big weight up a hill in one trip.

 

 

Essentials

Objects with engines convert energy even when travelling at a constant speed, due to the resistive forces acting.

\(P={W\over t}=F{s\over t}=Fv\)

This equation enables us to calculate the power of an object moving at constant speed, v, where F is either the thrust or resistive force.

 

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Exam-style Questions

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