Concise Selina Solutions for Class 10 Physics Chapter 2 Work, Energy and Power


Power is defined as the rate of doing work. It is a scalar quantity. Also, when work is done, an equal amount of energy is consumed. Thus, power is also defined as the rate at which energy is consumed or utilised.

The everyday meaning of work is some activity that requires physical or mental effort. But according to physics, the definition of work is more precise and unambiguous. In Physics, if a force displaces an object, the work is said to be done.

The SI unit of work done = Newton (N) X metre (m) = joule (J)

Energy is the capacity to do work. Energy is the cause and work is an effect. Therefore both work and energy have the same units, which is the joule (J) in the SI system and erg in the CGS system. Kinetic energy and potential energy are the two main types of energy.

Power is the work done in a unit of time. In other words, power is a measure of how quickly work can be done. The unit of power is the Watt = 1 Joule/ 1 second.