A flywheel is a solid, rotating disk that is sometimes used to store energy. The

Question

A flywheel is a solid, rotating disk that is sometimes used to store energy. The moment of inertia for a solid disk is 1/2MR^2 where M is the mass and R is the radius. If a flywheel weighs 10kg and has a radius of 0.4m, determine the following. A) If a point on the outside of the disk is moving at 12 m/s, what is the angular velocity of the flywheel? B) If the flywheel starts from rest and accelerates at a constant rate for 100 s to bring it up to the angular velocity found in Part A, what is the angular acceleration? C) If the angular acceleration in Part B is generated by a constant force applied tangentially to the outside edge of the disk (as shown below), what is the magnitude of the force?

Explanation / Answer

A)

w = angular velocity = V/R = 12/.4 = 30 rad/s

B)

w = alpha*t

angular acceleration = w/t = .3 rad/s^2

C)

Torque = I*alpha

F*R = I*alpha

F = MR * alpha/2 = .6 N

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