The tub within a washer goes into its spin cycle, starting from rest and reaching an angular speed of 16π rad/s in 7.2 s. At this point, the lid is opened, and a safety switch turns off the washer. The tub slows to rest in 16.7 s. Through how many revolutions does the tub turn? Assume constant angular acceleration while the machine is starting and stopping. Answer in units of rev

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The tub of a washer goes into its spin-dry cycle, starting from rest and reaching an angular speed of 6.0 rev/s in 9.0 s. At this point, the person doing the laundry opens the lid, and a safety switch turns off the washer. The tub slows to rest in 9.0 s. Through how many revolutions does the tub turn during this 18 s interval? Assume constant angular acceleration while it is starting and stopping.

we use the equation

angular displacement = w0 t + 1/2 at^2

where w0=initial ang vel a=ang accel t=time

we first find ang accel from

ang accel = (change in ang vel)/time = 6rev/s/9s

6 rev/s = 6x2pi rad/s , a = 4.19rad/s/s

the initial speed starting up is 0, so for the first 9 secs we have

ang displacment =1/2(4.19rad/s/s)(9s)^2=169.7 rad

in the second 9 s, the tub has a speed of 6 rev/s (=37.7rad/s, and we use this as the initial vel of the interval) we have

ang displacement = 37.7rad/sx9s - 1/2(4.19rad/s/s)(9s)^2 = 339.1rad - 169.7 rad

so the total displacement is 339.1 rad

same question as you posted......values changed only....try it

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Jun 23rd, 2015

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