Question

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

A
4 s
B
2 s
C
8 s
D
10 s

Solution

## The correct option is D 2 s $$I=1.2\ kgm^2$$$$\alpha =25\ rad/s^2$$$$KE = \dfrac{1}{2} I {\omega}^2$$$$1500 = \dfrac{1}{2}\times 1.2\times {\omega}^2$$$$50 rad/s = \omega$$$$\alpha =25\ rad/s^2$$$$\omega=0+\alpha t$$$$\dfrac{50}{25}=t=2\ sec$$  Physics

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