Question

Is energy scalar or vector?

Answer 1

In physics, we talk mainly about two types of quantities: a vector quantity and a scalar quantity. A scalar quantity is one which does not have any direction but only a magnitude. A vector quantity is one which has both direction as well as a magnitude.

Complete answer:
Some physical quantities can be completely described by just their magnitude. Such quantities are known as scalar quantities. These quantities can be added or subtracted from each other by simple rules of algebra. For example: mass of a body, speed of a body, etc.

But there are certain physical quantities which cannot be described by just their magnitude but also require some knowledge of their direction to get their complete knowledge. Such quantities are known as vectors. For example: velocity of a body, acceleration of a body, etc.

The energy of a body can be defined as the work done by that body. It is a scalar quantity because we just need the magnitude of energy while it does not possess any direction. Same is the case with work as work and energy are equivalent terms. They are actually derived from vector quantities of force and displacement by taking their scalar product.

$W = \overrightarrow F .\overrightarrow d$
Hence, the correct answer is that energy is NOT a vector quantity.

Note:
1. The energy can flow from one body to another but it is not a vector property. When we talk of the flow of energy, it does not imply that it is a vector quantity.
2. Unlike velocity and speed, energy does not have a vector counterpart. We do not need any information about direction while talking about energy.