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phy 201

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Testijg

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I dont understand the usage of torque when it comes to a rotating objest such as a disk? , honestly i dont understand the mathematics behind getting the velocity and ke on a rotating objest

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Just as force accelerates an object along a straight line, it's torque that results in the angular acceleration of a rotating object.

Just as mass resists the accelerating effect of net force, moment of inertia resists angular acceleration due to a net torque.

Newton's Second law therefore has two forms:

F_net = m a

tau_net = I alpha

where tau_net is net torque, I is moment of inertia and alpha is angular acceleration.

Furthermore, just as we find the work done by a force by multiplying the force by the displacement in the direction of the force, to get the work done by a torque we multiply the torque by the angular displacement in the direction of the torque.

So we have

`dW = F * `ds_parallel

`dW = tau * `dTheta_parallel.

The angular KE of a rotating object is

KE = 1/2 I omega^2,

just as the KE of a mass is 1/2 m v^2.

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