A cooling fan is turned off when it is running at 870 r e v / m i n . It turns 7

ID: 2144597 • Letter: A

Question

A cooling fan is turned off when it is running at 870rev/min . It turns 700 revolutions before it comes to a stop.

What was the fan's angular acceleration, assumed constant?

How long did it take the fan to come to a complete stop?

The tires of a car make 69 revolutions as the car reduces its speed uniformly from 92km/h to 40km/h . The tires have a diameter of 0.80m .

What was the angular acceleration of the tires?

If the car continues to decelerate at this rate, how much more time is required for it to stop?

2 questions in one problem for 300 is too less point

Solving only the first part:

wo = (870 * 2 * pi)/60 = 91.11 rad/s

s(angle turned) = 700 * 2 * pi = 4398.23 radians

wf = 0

wf^2 = wo^2 + 2(alpha)s

0 = 91.11^2 + alpha * 2 * 4398.23

alpha = -(91.11^2)/(2 * 4398.23) = -0.943 rad/s^2 (angular acceleration)

wf = wo + alph * t

t = -91.11/(-0.943) = 96.62 seconds

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