Physical Quantity MCQ - Practice Questions with Answers

• A quantity that can be measured and expressed in the form of laws is called a Physical quantity. 

• A physical quantity is expressed completely by its magnitude and unit   

• One physical quantity can be represented in terms of one or more units.   

 $\begin{aligned} & Q=n u \\ & \qquad \begin{array}{l}n=\text { numerical value or magnitude } \\ \\ u=\text { unit }\end{array}\end{aligned}$

• For a physical quantity

               nu =constant

         $\begin{aligned} & \text { So } n_1 u_1=n_2 u_2=\text { constant } \\ & \text { So } n \alpha \frac{1}{u}\end{aligned}$

            So, the Larger the unit, the smaller the magnitude.

• Types of the physical quantity 

1) Scalar Quantity

The quantities having magnitude only are known as scalar quantities.

 It does not specify the direction.

Scalar quantity can be added or subtracted by the laws of addition or subtraction

Examples are time, work, energy, etc......

2) Vector Quantity

The quantities having both directions as well as magnitude are known as vector quantities.

It has a specific direction.

Vector quantity can be added and subtracted according to vector laws of addition.

Examples - Displacement, force, velocity, acceleration, momentum ....etc.

3) Tensor Quantity

  Scalar and vector are special cases of a tensor.

Tensors are represented in the multi-dimensional array, i.e., in different directions, tensor will have different magnitudes.

1. If a tensor has only magnitude and no direction, it is called a  scalar

2. If a tensor has magnitude and one direction, it is called a vector.

 Examples- Stress, The moment of inertia, coefficient of viscosity

4) Ratio Quantity

When a physical quantity is the ratio of two similar quantities.

eg. Relative density $=\frac{\text { density of object }}{\text { density of waterat } 4^{\circ} \mathrm{C}}$