Question

A tangential force of 10 N is applied on the periphery of a ring due to which it starts rotating about an axis through its centre and perpendicular to its plane. What is the work done by this force in rotating the ring by ${45}^o$? {R = 2m}.

• A. $4\pi J$
• B. $5\pi J$
• C. $10\pi J$
• D. $15\pi J$

Answer 1

The correct option is B $5\pi J$

Torque produced = rF = 20 N-m
Angle rotated = ${45}^o=\frac{\pi }{4}radians$
Work done $=\tau \theta =\frac{20\pi }{4}=5\pi J.$