### What friction torque is required to reduce angular speed

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##### Reference no: EM134395

Question1

When the door of the Chapel of the Mausoleum in Hamilton, Scotland, is slammed shut; the last echo heard by someone standing just inside the door reportedly comes 22.0 s later.

(a) If that echo were due to a single reflection off a wall opposite the door, how far from the door would that wall be (in km)?

(b) If, instead, wall is 27.1 m away, how many reflections (back and forth) correspond to last echo? Imagine the speed of sound is 345 m/s.

Question2

A uniform spherical shell of mass 8.10kg with diameter 48.0cm has four small masses of mass 1.80kg attached to its outer surface and regularly spaced around it. This combination is spinning about an axis running throughout the center of the sphere and two of the small masses. What friction torque is required to reduce its angular speed from 77.0rpm to 55.0rpm in a time interval of 34.0s?

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