Define Power in Terms of Physics

We all are familiar with the word power. In our daily life power is usually related to taking decision and implementation. In science the word “power” is related to the devices motor, pump, and engine etc. i.e. any device that can work. Sometimes we want to solve any task quickly.

Suppose we want to fill a water tank on the roof of a multistoried building taking water from its reservoir at the ground floor or from a pond. It takes a lot of time if we want to fill the tank carrying water with a bucket. It takes less time to fill the tank with the help of a motor or a pump. Sometimes a work is done quickly or slowly. Power is the measure of a source by which how fast or how slow a source can work is measured. Suppose two friends-Roth and Oni live on the fifth floor of a building. The mass of the two friends is the same. Coming to the lift at the ground floor they found the lift not working. They had to use the stairs to go up the building. Roth took 40 seconds and Oni took 80 seconds to reach the 5th floor. We say Roth has more power than Oni.

Though both of them has done same amount of work to reach the same height Roth has more power because he has done the work faster. Power is the rate of doing work or transformation of energy. Power of a person or a source is measured by the amount of work done per unit time.

Power = Work / Time

If as person or a device can do W amount of work or transform energy at time it then the power P will be,

P = W / t

Power has no direction. So it is a scalar quantity.

Dimension: The dimension of power is the dimension of Work / Time  

Power = Work / Time = (Force x Displacement) / time = (Mass x Acceleration x Displacement) / time = (Mass x Displacement x Displacement) / (time * time2)

= (Mass x Displacement2) / (time3)

So, [P] = M L2 / T2 or [ML2 T-3]