A heavy cast iron flywheel rotates at a constant speed of 150rev/min. A friction

Question

A heavy cast iron flywheel rotates at a constant speed of 150rev/min. A friction braking system is used to bring the flywheel torest. When the flywheel is braked, it experience a constantretarding moment of 5 N m. The mass moment of inertia of theflywheel about its center axis is a 6.25 kg m3. Use workand Energy to determine how many revolutions it takes before theflywheel comes to rest. Solve the same problem, but use a massmoment of inertia of 16 kg m3. Compare the requiredrevolutions for them to stop.

Explanation / Answer

Becuase we are given the moment exerted by the braking system andthe moment of inertia of the flywheel, we cause use the formula = I to determine the angular acceleration of theflywheel (negative since its slowing down). = /I = 0.8 rad/s2 since i = 150 rev/min = 15.708 rad/s and f = 0 we can use thatf2=i2 +2 where is what we want to find, plugging in we get: 0 = 15.7082 - 2*0.8* therefore, = 154.213 rad = 24.544 rev That is the answer to the first part. For the second part, wereplace the value of I with 16 which gives us: = 0.3125 rad/s2 i = 150 rev/min = 15.708 rad/s f = 0 so we get 0 = 15.7082 - 2*0.3125* and thus = 394.786rad = 62.832 rev

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