# physics

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A disk rotates about its central axis starting from rest and accelerates with constant angular acceleration. At one time it is rotating at 7 rev/s. 55 revolutions later, its angular speed is 21 rev/s.
(a) Calculate the angular acceleration.
(b) Calculate the time required to complete the 55 revolutions mentioned.
(c) Calculate the time required to attain the 7 rev/s angular speed.
(d) Calculate the number of revolutions from rest until the time the disk attained the 7 rev/s angular speed.

This is pretty straighforward. What is about it that you do not understand?

what equations do I use? thanks for your help.

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