Question

The degree of freedom of a stationary rigid body about its axis will be:

(A) one
(B) two
(C) three
(D) four

Answer 1

Hint:In order to find out the degree of freedom of a stationary rigid body about its axis, first we need to understand what is degree of freedom of a particle or a body in physics and how it is being calculated for different-different body or particle then only we can get the required answer.


Complete answer:
Now, first start with the basic knowledge about the degree of freedom:
Degree of freedom of a body or particle is the number of independent ways in which the body or molecule can move. We can also include in which a body or particle rotates or vibrates in space.
A degree of freedom of a body or particle is a physical quantity and is also independent.
In order to locate a particle in three dimensional space, it requires three coordinates for the position. Similarly, the direction in which a particle moves and the speed with which it moves can be described in terms of three velocity components, each in reference to the three dimensional space.

Also the kinetic energy of a particle or body in motion is depended on the degree of freedom:
$K = \dfrac{{fRT}}{2}$
Where, K is kinetic energy
f is the degree of freedom of the particle or body
R s gas constant
T is temperature

Now, for the stationary rigid body given in the question:
A stationary rigid body can move or vibrate in three dimensional space in 3 directions, which are mutually perpendicular to each other. Therefore, its degree of freedom will be three (3).

Hence the correct answer is Option(C).



Note: Have the basic idea of what is the degree of freedom of a particle or body in a three dimensional space and how it is being calculated. Use the same for the given question that is for a stationary rigid body about its axis and finally get the required answer that is its degree of freedom which is 3 here.