a)
kinetic energy stored in the fly wheel is
        K.E = 1/2
I?2Â Â Â Â .=1/2((1/2) MR2)
w^2
                              Â
= (1/2)(1/2) (600 kg)(1.5 m)2(4000 rev / min) ( 2 pi/ 60
rad))^2
                     Â
=59157600 J
(b)
power P = 15 hp
             =
746*15 W
           Â
= 11190 W
power P = energy/time
therefore ,
           Â
time t = energy/power
                    Â
= 59157600 J/ 11190 W
                    Â
= 5286.64s( 1h/ 3600 s)
                   Â
=1.46 hr
