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Q7.12     A solid cylinder of mass  20 kg rotates about its axis with angular speed 100 \: rad\: s^{-1}. The radius of the cylinder is 0.25m . What is the kinetic energy associated with the rotation of the cylinder? What is the magnitude of angular momentum of the cylinder about its axis?

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Firstly we will calculate moment of inertia of the solid cyliner : 

                                               I_c\ =\ \frac{1}{2}mr^2

                                                      =\ \frac{1}{2}(20)(0.25)^2\ =\ 0.625\ Kg\ m^2

So the kinetic energy is given by : 

                                             E_k\ =\ \frac{1}{2}I\omega ^2

                                                       =\ \frac{1}{2}\times (6.25)\times (100) ^2

                                                       =\ 3125\ J

And the angular momentum is given by :     =\ I\omega

                                                                     =\ 0.625\times 100

                                                                     =\ 62.5\ Js

Posted by

Devendra Khairwa

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