A centrifuge is a common laboratory instrument that separates components of diff

Question

A centrifuge is a common laboratory instrument that separates components of differing densities in solution. This is accomplished by spinning a sample around in a circle with a large angular speed. Suppose that after a centrifuge in a medical laboratory is turned off, it continues to rotate with a constant angular deceleration for 10.4 s before coming to rest. Part A If its initial angular speed was 3900 rpm , what is the magnitude of its angular deceleration? Part B How many revolutions did the centrifuge complete after being turned off?

I got A) 39.27 rev/s^2 and B) 3335.81 rev and both were wrong. Please help.

Problem 10.22 Part A A centrifuge is a common laboratory instrument that separates components of differing densities in solution. This is accomplished by spinning a sample around in a circle with a large angular speed. Suppose that after a centrifuge in a medical laboratory is turned off, it continues to rotate with a constant angular deceleration for 10.4 s before coming to rest. If its initial angular speed was 3900 rpm, what is the magnitude of its angular deceleration? lal= 39.27 rev/s- Submit My Answers Give Up Incorrect; Try Again; 3 attempts remaining Part B How many revolutions did the centrifuge complete after being turned off? 6-13335.81 rev Submit My Answers Give Up Incorrect; Try Again; 5 attempts remaining Provide Feedback Continue

Explanation / Answer

A. wi = 3900 rpm = 408.41 rad/sec

wf = 0

t = 10.4 sec

wf = wi + alpha*t

alpha = -wi/t

alpha = -408.41/10.4 = 39.27 rad/sec^2 = 39.27/2*pi = 6.25 rev/sec^2

B.

theta = wi*t + 0.5*alpha*t^2

theta = 408.41*10.4 - 0.5*39.27*10.4^2

theta = 2123.74 rad = 2123.74/(2*pi) = 338 rev

your method was right but you didn't use correct units of variables

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