A 13.0 kg wheel, essentially a thin hoop with radius 2.10 m, is rotating at 352

Question

A 13.0 kg wheel, essentially a thin hoop with radius 2.10 m, is rotating at 352 rev/min. It must be brought to a stop in 30.0 s. (a) How much work must be done to stop it? (b) What is the required average power? Give absolute values for both parts.

Chapter 10, Problem 061 A 13.0 kg wheel, essentially a thin hoop with radius 2.10 m, is rotating at 352 rev/min. It must be brought to a stop in 30.0 s. (a) H much work must be done to stop it? (b) What is the required average power ow Give absolute values for both parts. (a) Number Units. (b) Number nits Click if you would like to show work for this question Open Show Work

Explanation / Answer

Mass of the wheel M = 13 Kg

Radius r = 2.10 m

Initial angular speed 1 = 2(352/60) = 36.86 rad/s

Final anular speed 2 = 0

time t = 30 s

Moment of inertia I = Mr^2 = 57.33 Kg m^2

(a)

Work done W = (1/2)I(12 - 22)

                     = 0.5*57.33( 36.86)2

                     = 38945.97 J

(b)

Average power P = W/t = 38945.97/30 = 1298.19 watt

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