Practice portal › Rotational Motion › Rotational Dynamics

Two rotating bodies A and B of masses m and 2m with moments of inertia I_A and I_B (I_B>I_A) have equal kinetic energy of rotation. If L_A and L_B be their angular momenta respectively, then

Asked in NEET-II 2016 · Rotational energy and released bodies

Answer: (3) L_B>L_A

Step-by-step solution

Given: K_A=K_B and I_B>I_A.

Idea: write the kinetic energy in terms of angular momentum, so the comparison turns on I alone.

K=1/2Iω² and L=Iω, so K=(L²)/(2I).

L=√2IK

With K the same for both, L increases with I.

I_B>I_A⇒ L_B>L_A. The masses play no part, since I is given directly.

Why the other options are wrong

More Rotational Dynamics questionsAll Rotational Dynamics questions →

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.

Practise this with a timer