COMEDK · Physics · 7. Center of Mass Momentum and Collision

Newton's second law of rotational motion of a system particles having angular momentum \(L\) is given by

A \(\dfrac{d p}{d t}=\tau_{\text {ext }}\)
B \(\dfrac{d L}{d t}=\tau_{\text {int }}\)
C \(\dfrac{d L}{d t}=\tau_{\text {ext }}\)
D \(\dfrac{d L}{d t}=\tau_{\mathrm{int}}+\tau_{\mathrm{ext}}\)

Verified Solution

Answer & Solution

Correct Answer

(C) \(\dfrac{d L}{d t}=\tau_{\text {ext }}\)

Step-by-step Solution

Detailed explanation

For a system of particles, the total angular momentum \(\vec{L}\) is the sum of the angular momenta of individual particles. The rate of change of the total angular momentum is given by the sum of the torques acting on the system. The total torque \(\vec{\tau}\) acting on the…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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