Question

Which of the following is not a scalar quantity?
A. Temperature
B. Coefficient of friction
C. Charge
D. Impulse

Answer 1

There are two types of quantity: scalar and vector. Scalar means only magnitude is present and in vector, magnitude and direction both are present. Quantity having magnitude only known as scalar quantity and quantity having both magnitude and direction is known as vector quantity. In question it is given that quantity is not scalar, it means it must be vector.

Complete step-by-step answer:
We know that there is a direction of temperature, coefficient and charge. So these are scalar quantities. They have only magnitude.
Now we will understand what is impulse then we will see why it is not a scalar quantity. Take a daily life example to understand what impulse is. Let’s take an example of badminton, a cork is hit by the ball or hammering on wood. These are all forces that act for a short interval of time. Therefore it is difficult to measure all those forces.
In such cases we measure the total effect of the force on the body which is called the impulse of the force. Consider an impulse force $\overrightarrow{f}$acting on a body of mass m for a short interval of time t. The velocity of the body changing from initial position $\overrightarrow{u}$ to final position $\overrightarrow{v}$.
Let $\overrightarrow{{{P}_{1}}}\And \overrightarrow{{{P}_{2}}}$ are initial and final linear momentum respectively.
Then according to Newton's law of motion.
$\overrightarrow{f}=\dfrac{\overrightarrow{{{P}_{2}}}-\overrightarrow{{{P}_{1}}}}{t}$
So we can say impulse of force of impulse $\overrightarrow{f}$.t=$\overrightarrow{{{P}_{2}}}-\overrightarrow{{{P}_{1}}}$.
Therefore$\overrightarrow{J}=\overrightarrow{mv}-\overrightarrow{mu}$. This implies it is equal to the change in linear momentum of the body. So we can say that Impulse is a vector having both direction and magnitude. Also since it is a type of force, and force is a vector quantity.

So, the correct answer is “Option D”.

Note: Students can remember the properties of impulse by knowing that it is a type of force and simply it is a force. Impulse is a vector having both direction and magnitude. Also since it is a type of force, and force is a vector quantity. Its direction is the same as that of force. The SI unit of impulse is newton second. It has the same unit as that of linear momentum. All the quantities given in option are scalar except impulse. Impulse is a type of force. Like force it has both magnitude and direction. The main point in impulse is, the duration of the effect of force is very small such that we are not able measure it. Temperature is a scalar quantity. It only measures quantity, it does not show direction or it doesn't have direction. Coefficient of friction has a magnitude quantity only. Charges too have magnitude only.