Question

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

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

In each rotation relative speed becomes zero twice and becomes maximum twice.