Question

The unit of energy is:
A: Newton
B: Kilogram
C: Joule
D: Watt

Answer 1

Hint : Energy can be defined as the quantitative measure that is to be transferred to a work to perform work on. In other words, we can define it as the capacity of a body to do work. It is available in a large variety of forms as well. We can derive the unit of energy using these facts.

Complete Step By Step Answer:
As mentioned in the hint, energy is nothing but the capacity of a body to do work. Since energy is expressed in terms of work, we can say that energy has the same unit as that of work.
Work done can be defined as the force required to cause a displacement in a body. In other words, it is the product of force and displacement.
$W = F \times d = (kgm{s^{ - 2}}) \times m = kg{m^2}{s^{ - 2}}$
Thus the unit of energy can also be expressed as $kg{m^2}{s^{ - 2}}$ .
However, this international unit is given in honour of the scientist who contributed to the development of the concept of energy. The name of the scientist was James Prescott Joule and honouring him, the SI unit of energy is given as ‘Joule’.
Thus, we can conclude that option C is the correct answer among the given options.

Note :
Energy is abundantly available in different forms including kinetic energy, potential energy, mechanical energy, electrical energy, thermal energy, heat energy and so on. All these quantities have the same SI unit and all of them are expressed in terms of joules. As the rest of the options we know that the unit of force is newton. The S.I unit for Mass is kilogram. The S.I unit of power is unit.