Question

The figure shows a uniform smooth solid cylinder A of radius 4 m rolling without slipping on the 8 kg plank which in turn is supported by a fixed smooth surface. Block B, is known to accelerate down with $6m/s^2$.
(Take g = $10m/s^2$)

If unwrapped length of the thread between the cylinder and block B is 20 m at the beginning, when the system was released from rest, what would it be 2 s later ?

• A. 28 m
• B. 30 m
• C. 22 m
• D. 32.5 m

Answer 1

The correct option is A 28 m

Length of thread $=20+\frac{1}{2}\left(R\alpha \right)t^2$
= 28 m.