Question

The rotational kinetic energy of a rigid body moment of inertia $5kg{m}^2$ is $10$ joules.The angular momentum about the axis of rotation would be :

• A. $100$ joule-sec
• B. $50$ joule-sec
• C. $10$ joule-sec
• D. $2$ joule-sec

Answer 1

The correct option is C $10$ joule-sec

Solution

We know,

$K{E}_{rotational}=\frac{1}{2}I{\omega }^2$

Here,

$105=\left(\frac{1}{2}\right)\left(5\right){\omega }^2$

$\Rightarrow {\omega }^2=4\Rightarrow \omega =2$ rad/s

We know,

$L=I\omega =\left(5\right)\left(2\right)=10J.S$

Option - C is correct.