Two identical discs of same radius `R` are rotating about their axes in opposite directions with the same constant angular speed `omega` . The discs are in the same horizontal plane. At time `t = 0` , the points `P` and `Q` are facing each other as shown in the figure. The relative speed between the two points `P` and `Q` is `v_(r)`. In one time period `(T) ` of rotation of the discs , `v_(r)` as a function of time is best represented by

Options

A.
B.
C.
D.

Answer

A

Explanation

In each rotation relative speed becomes zero twice and becomes maximum twice
Aliter : At t = 0 the relative velocity will be maximum in magnitude
At ` t = (T)/( 2)` the relative velocity will be zero
At `t = (3T)/( 2)` the relative velocity will be maximum in magnitude
At t = T the relative velocity again become zero