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NEET PHYSICSMedium

Two rotating bodies AA and BB of masses mm and 2m2m with moments of inertia IAI_A and IBI_B (IB>IAI_B > I_A) have equal kinetic energy of rotation. If LAL_A and LBL_B be their angular momenta respectively, then:

A

LA=LB2L_A = \frac{L_B}{2}

B

LA=2LBL_A = 2L_B

C

LB>LAL_B > L_A

D

LA>LBL_A > L_B

Step-by-Step Solution

The rotational kinetic energy (KK) is related to angular momentum (LL) and moment of inertia (II) by the relation K=L22IK = \frac{L^2}{2I}. Given that the kinetic energies of rotation are equal: KA=KBK_A = K_B. LA22IA=LB22IB\frac{L_A^2}{2I_A} = \frac{L_B^2}{2I_B} Rearranging the terms, we get: LB2LA2=IBIA\frac{L_B^2}{L_A^2} = \frac{I_B}{I_A} It is given that IB>IAI_B > I_A, so the ratio IBIA>1\frac{I_B}{I_A} > 1. Therefore, LB2LA2>1    LB2>LA2    LB>LA\frac{L_B^2}{L_A^2} > 1 \implies L_B^2 > L_A^2 \implies L_B > L_A.

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