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Power in physics 1. The time rate of doing  work  is called power. If W is the amount of work done in time t, then average power, Pav=W/t. Power in physics 2. Because power is the ratio of two  scalars , the average power is a scalar. 3. The power of an agent during a time interval may not be constant. The instantaneous power is defined as the limiting value of the average power of an agent in a small time interval, when the time interval approaches zero. Hence, if ΔW is the small amount of work done in a small time interval Δt, then instantaneous power is defined as: P=dW/dt Now, dW=F.ds P=F.(ds/dt) But ds/dt=v, the instantaneous  velocity of the particle . Therefore, P = F. v Thus, instantaneous power of an agent is measured as the dot product of instantaneous velocity and  force  acting on it at the instant. If θ is the angle between F and v, then P =Fv cosθ In case, θ =0 P =Fv 4. Dimension and unit of power a) [P]=[W]/[t]=[ML 2...