The tub of a washer goes into its spin-drycycle, starting from rest and reaching

Question

The tub of a washer goes into its spin-drycycle, starting from rest and reaching an angular speed of2.0 rev/s in 8.0s. At this point, the person doing the laundry opens the lid, and asafety switch turns off the washer. The tub slows to rest in10.0 s. Through how many revolutions doesthe tub turn during this 18 s interval?Assume constant angular acceleration while it is starting andstopping.
Enter anumber. 1 rev
The tub of a washer goes into its spin-drycycle, starting from rest and reaching an angular speed of2.0 rev/s in 8.0s. At this point, the person doing the laundry opens the lid, and asafety switch turns off the washer. The tub slows to rest in10.0 s. Through how many revolutions doesthe tub turn during this 18 s interval?Assume constant angular acceleration while it is starting andstopping.
Enter anumber. 1 rev
Enter anumber.

Explanation / Answer

assume constant angular acceleration at start andstop

SPEED UP
Velocity (vi) = 0 rev/s
Velocity (vf) = 2 rev/s
Time (t) = 8s

x = 1/2 ( vi + vf ) * t
x = 1/2 ( 0 + 2 ) * 8
x = 8 rev

SLOW DOWN
Velocity (vi) = 2 rev/s
Velocity (vf) = 0 rev/s
Time (t) = 10s

x = 1/2 ( vi + vf ) * t
x = 1/2 ( 0 + 2 ) * 10
x = 10 rev

Total revolutions in 18 seconds:
8 + 10 = 18 rev

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