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The tub of a washer goes into its spin cycle, starting from rest and gainiing angular speed steadily for 8.0 s when it is turning at 5.0 rev/s. At this time the person doing the laundry opens the lid and a safety switch turns off the washer. The tub smoothly slows to rest in 12.0 s. Through how many revolutions does the tub turn whil it is in motion.

Respuesta :

HomertheGenius
Angular acceleration is change of angular velocity over time:
α = 5 / 8 = 0.625 rev / s²
Number of revolutions of the 1st part:
α · t² /2 = 0.625 * 8² / 2 = 20 rev.
The 2nd part:
α = 5/12 = 0.41667 rev/s²
5 * 12 - ( 0.41667 * 12² / 2 ) = 60 - 30 = 30 rev.
In total: 20 + 30 = 50 revolutions 

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