Question

A flywheel is making $\frac{3000}{\pi }$ revolution per minute about its axis. If the moment of inertia of the flywheel about that axis is $400{kgm}^2$, its rotational kinetic energy is

• A. $2\times {10}^{6}J$
• B. $3\times {10}^{3}J$
• C. $500{\pi }^{2}J$
• D. $12\times {10}^{3}J$

Answer 1

The correct option is A $2\times {10}^{6}J$

Given $I=400kg{m}^2$, $N=\frac{3000}{\pi }rpm$

$\therefore \omega =\frac{2\pi N}{60}=100rad/s$

Rotational Energy $=\frac{1}{2}I{\omega }^2$

$\Rightarrow \text{Rotational Energy}=\frac{1}{2}\times 400\times {100}^2=2\times {10}^{6}J$