Answer:

Explanation:
As we know that initial angular speed of the tub was zero and then it increases uniformly to 4 rev/s in t = 6.00 s
so we will have




Now when the tub will comes to rest uniformly after opening the lid in time interval of t = 15 s
then we have




Now total angular displacement of the tub is given as



so number of revolutions is given as


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