The Tub of a washer goes into a spin cycle, starting from rest and gaining angular speed steadily for 8 s, when it is turning at 5 rev/s. At this point the person doing the laundry opens the lid, and a safety switch turns off the washer. The tub smoothly slows to rest in 12s. Through how many revolutions does the Tub turn while it is in motion? Ok, I am going to do this problem in 2 stages: One for Wi =0 and Wf=5 rev/s and the second for Wi=5rev/s and W[size=.5]f[/size]=0 First stage: Known Wi=0 Wf=5 rev/s T=0 T=8s Oi=0 Unknown A=? Of=? Wf= (5 rev/s)(2(pi)rad/rev) Wf= 10(pi) rad or 31.4 rad A = (Wf-Wi)/T A = 31.4/8 A = 3.9 rad/(s^2) Of=Oi+(Wi(T)+.5(A)(T)^2 Of= 0 + (10)(pi)(8) + .5(3.9)(8)^2 Of= 80(pi) + 40(pi) Of= 377 rad (I am going to leave it in this form because I am going to have to plug it into stage two. Stage two: Known Wf= 0 Wi= 5 rev/s or 10(pi) rad/s Oi= 377 rad (found in stage one) T=12 s Unkown A=? Of=? A = (Wf-Wi)/T A = (0-31.4)/12 A = -2.6 rad/s^2 Of=Oi+(Wi)(T)+.5(A)(T)^2 Of= 377 + 31.4(12) + .5(-2.6)(12)^2 Of= 377 + 376.8 - 187.2 Of=566.8 rad Now we need to convert to revolutions: 566.8 rad(57.3/rad)= 32477.64 degrees 32477.64/(360/rev) = 90. 2 rev Ok here is what I do not get. My revolutions for the washer when its acceleration is increasing in stage one is slower than the revolutions when the acceleration is decreasing in stage two. I think I am correct but it doesn't make sense.