Question

The unit of energy is
(A). Newton
(B). Kilogram
(C). Joule
(D). Watt

Answer 1

Hint: Energy is defined as the ability of a body to do work. Work is the product of force and displacement. Energy is stored in a body when work is being done on it. Energy is a scalar quantity. The more energy a body possesses, the more unstable it is. The equilibrium position is the one in which energy is minimum

Complete answer:
The magnitude of the product between force and displacement is known as work. Its SI unit is joules ($J$). It is given as-
$W=\vec{F}\cdot \vec{x}$
Here, $W$ is the work done
$\vec{F}$ is the force vector
$\vec{x}$ is the displacement vector
From the above equation, we can see that work is the scalar product of vectors, force and displacement.
When work is done on a body, it is stored in it as energy. Now work can be done on a body by virtue of its position or by virtue of its motion.
When work is being done on the body by virtue of its position, potential energy is stored in it. When a body accelerates, a force does work on it and kinetic energy is stored by virtue of that work.
Since the work is converted and stored as energy in a body, the SI unit of energy is the same as work done, that is, the SI unit of energy is joules.
Therefore, the unit of energy is joules.

Hence, the correct option is (C).

Note:
When a dot product of two vectors is taken, their resultant is a scalar. Work and energy are path functions; this means they depend on the initial and final states and not on the path taken. When the body does work, then the energy stored in it is used to perform work. Potential energy is always negative.