Question

The frictional force can’t be measured in
A. kg wt
B. newton
C. dyne
D. kg \[m{{s}^{-1}}\]

Answer 1

Hint: In this question we have been given different units in options and we have been asked to state the unit in which the frictional force can not be measured. Therefore, to answer this question, we shall first find the dimensions of frictional force as well as the unit of the frictional force. We know that friction force is taken as the product or normal force and the coefficient of friction.

Complete answer:
We know that friction force is given as the product of coefficient of friction and the normal reaction force.
\[F=\mu N\]
Where, \[\mu \]is the coefficient of friction
It is clear that the friction force will have the dimension of force. We know that the unit of force is Newton in the SI system and dyne in the CGS system. Therefore, friction force will always be measured in Newtons or dynes.
Now, we know that
\[F=ma\]
The dimensions of force can be given as,
\[\left[ F \right]=\left[ kgm{{s}^{-2}} \right]\]
So, we can say that, from the given options, the last option does not match the dimensions of force.
Therefore, the friction force can not be measured in kg \[m{{s}^{-1}}\].

So,the correct Option is D.

Note:
The friction force is the force opposing the motion of an object. It is the force exerted by the surface as an object moves across it. There are two types of friction force namely static and dynamic friction. The static friction is greater than dynamic friction. When an object is in motion the resistance offered by the surface is known as the dynamic friction.