Question

The moment of inertia of a body about a given axis is $1.2kg{m}^2$. Initially the body is at rest. In order to produce a rotational kinetic energy of 1500J, an angular acceleration of $25rad/se{c}^2$ must be applied about that axis for a duration of:

• A. 4s
• B. 2s
• C. 8s
• D. 10s

Answer 1

The correct option is B 2s

Kinetic energy of rotation $=\frac{1}{2}I{\omega }^{2}1500=\frac{1}{2}\times 1.2{\omega }^2\omega =50rad/sec\omega -{\omega }_0=\alpha t50-0=25t=2sec.$