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Q.
For a system of particles if $\tau_{\text {ext }}=0,$ then choose the correct option:
System of Particles and Rotational Motion
Solution:
If $\tau_{\text {ext }}=0,$ then
$\frac{ dL }{ dt }=0$
$L =\text { constant }$
If $\tau_{\text {ext }}$ is zero, then the total angular momentum of the system remains conserved. Conservation of angular momentum is rotational analogue of conservation of linear momentum