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A grindstone, originally rotating at 126 rad/s undergoes a constant angular acceleration so that it makes 20.0 rev in the first 8.00s. What is the angular acceleration?

a) 0.313 rad/s2

b) 0.625 rad/s2

c) 2.50 rad/s2

d) 1.97 rad/s2

e) 13.79 rad/s2

My Calculations:

20rev*2PIrad/rev = 40PI rad = theta

t = 8 sec

wo = 126 rad/sec

theta = wo*t+1/2*a*t^2

40PI = 126*8+.5*a*8^2

40PI-126*8 = 32a

a = -27.57 rad/sec^2

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# Homework Help: Angular Acceleration and a grindstone

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