Power #8211; The time rate of doing work is called power. i.e. Power, P = d W/dt For a constant force F, the power P = F times; v ⇒ P = Fvcosθ where, v = Velocity of object, θ is angle between F and v. It is a scalar quantity. SI unit of power is watt and its practical unit is Horse Power (HP). 1 HP = 746 W