System of Particles and Rotational Motion - Result Question 43

46. A disc is rotating with angular velocity $\omega$. If a child sits on it, what is conserved ?

[2002]

(a) Linear momentum

(b) Angular momentum

(c) Kinetic energy

(d) Moment of inertia

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Answer:

Correct Answer: 46. (b)

Solution:

  1. (b) If external torque is zero, angular momentum remains conserved.

$L=I \omega=$ constant

External torque is zero because the weight of child acts downward