Question

Why do we say that pressure is a scalar quantity?
(a) Pressure has both magnitude and direction.
(b) Pressure has magnitude but no specific direction.
(c) Pressure has no magnitude and no direction.
(d) Pressure has no magnitude and a specific direction.

Answer 1

- Hint – In this question use the basic concept that a vector is quantity that has both direction as well as magnitude, however a scalar quantity has only magnitude and no direction. So think of pressure, can it have a direction? If not then surely it will be a scalar else it will be a vector. This approach will help to get the right answer.

Complete step-by-step solution -

As we know scalar quantity has magnitude only (i.e. it has no direction).
As we see when a particular body or any other material is immersed in water or any other fluid then pressure is exerted from all sides and not any particular direction.
So we can say that pressure has magnitude but no particular direction so it follows the rule of a scalar quantity.
Hence pressure is a scalar quantity.
So pressure has magnitude but no specific direction.
Hence option (B) is the correct answer.

Note – There is a misconception that pressure is force acting per unit area and force is a vector as it has both magnitude as well as direction thus pressure should be vector only. This is entirely wrong as the categorization of a quantity to be a vector or a scalar is completely independent upon the categorization of its dependencies. This needs to be in mind while solving problems of this kind.