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 KE of $1500J$, an angular acceleration of $25rad/se{c}^2$ must be applied about that axis for a duration of:

• A. 4 s
• B. 2 s
• C. 8 s
• D. 10 s

Answer 1

Answer: (B)

2 s

$I=1.2kg{m}^2$

$\alpha =25rad/s^2$

$KE=\frac{1}{2}I{\omega }^2$

$1500=\frac{1}{2}\times 1.2\times {\omega }^2$

$50rad/s=\omega$

$\alpha =25rad/s^2$

$\omega =0+\alpha t$

$\frac{50}{25}=t=2sec$