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Rotational analogue of Newton’ s second law for the translational motion of a single particle: dl / st = τ
Torque and angular momentum of system of particles: o
The total angular momentum of a system of particles about a given point is addition of the angular momenta of individual particles added vectorially. o
Similarly for total torque on a system of particles is addition of the torque on an individual particle added vectorially.
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The torque resulting from internal forces is zero, due to o Newton’ s third law i. e. these forces are equal and opposite. o o
These forces act on the line joining any two particles
The time rate of the total angular momentum of a system of particles about a point is equal to the sum of the external torques acting on the
system taken about the same point.
Conservation of Angular Momentum o
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if the total external torque on a system of particles is zero, then the total angular momentum of the system is conserved
If text = 0, then dL / dt = 0 => L = constant