Derive the Relation between Torque and Angular momentum ?

Explanation

Angular momentum(L) : It is an measure of the rotation of body, taking into account its mass , shape and speed.

L = r × p
where r is distance from the axis of rotation and the p is the linear momentum of the body.

Torque (τ) : It is an moment of force i.e. tendency of a force to rotate an object about an axis.

τ = r × f
where r is the perpendicular distance from the axis of the rotation and f is the applied force.

As we know ,

L = r × p

differentiating both sides with respect to t

dL/dt = r × (d p / dt)  + p × (d r / dt)

dL/dt = r × f  + m(v × v)

dL/dt = τ + 0

τ = dL/dt

Hence , the relationship between torque and angular momentum.

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