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n electric motor rotating a workshop grinding wheel at a rate of 94 rev/min is switched off. Assume constant negative angular acceleration of magnitude 1.70 rad/s. (a) How long does it take for the grinding wheel to stop? (b) Through how many radians has the wheel turned during the interval found in (a)? rad

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Answer:

a) It takes 5.79 seconds for the grinding wheel to stop.

b) In an interval of 5.79 seconds it rotates 28.48 rad.

Explanation:

a) We have equation of motion v = u + at

  Here v = 0 rad/s, a = -1.70 rad/s², u = 94 rev/min = 9.84 rad/s

  Substituting

         0 = 9.84 - 1.70 x t

          t = 5.79 seconds.

It takes 5.79 seconds for the grinding wheel to stop.

b) We have equation of motion v² = u² + 2as

      v = 0 rad/s, a = -1.70 rad/s², u = 9.84 rad/s

  Substituting

         0² = 9.84² - 2 x 1.70 x s

          s = 28.48 rad

 So in an interval of 5.79 seconds it rotates 28.48 rad.

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