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## How is power related to force and velocity?

It is some time convenient to express power in terms of constant force (F) acting on an object moving at constant velocity “V” .

For example when the propeller of motor boat causes the water to exert constant force on the boat,it moves with constant velocity v .The power delivered by motor at any instant is:

Power is the dot product of force and velocity.It is a scalar quantity.The SI unit of power is watt which is defined as “One joule of work done in one second.”

Sometimes in the electrical measurements the unit is expressed as watt second.However the commercial unit of electrical energy is killowatt hour.One killowatt hour is the work done in one hour by an agency whose power is one killowatt.

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