JEE Main2017PhysicsRotational MotionActual
A uniform disc of radius R and mass M is free to rotate only about its axis. A string is wrapped over its rim and a body of mass m is tied to the free end of the string as shown in the figure. The body is released from rest. Then the acceleration of the body is:
Options
- A2   M g 2 m + M
- B2 M g 2 M + m
- C2 m g 2 M + m
- D2 m g 2 m + M
Correct answer
D. 2 m g 2 m + M
Step-by-step solution
m g - T = m a R T = I α R T = M R 2 2   . a R T = M a 2 m g - M a 2 =   m a m g = a M 2 + m m g = a   M + 2 m 2 a = 2 m g M + 2 m