Q.
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 figure. The relative speed between the two points $P$ and $Q$ is $V_{r}$ as function of times best represented by
A) [image:4_image57.emf]
B) [image:4_image58.emf]
C) [image:4_image59.emf]
D) [image:4_image60.emf]
Explanation
(a) [image:4_image152.emf]
So, $V_{r} = 2\omega R\sin{(\omega t)}$
At $t = T/2,\ V_{r} = 0$
So two half cycles will take place
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.