A car is designed to get its energy from a rotating flywheel (soliddisk) with a

Question

A car is designed to get its energy from a rotating flywheel (soliddisk) with a radius of 1.00 m and a massof 550 kg. Before a trip, the flywheel isattached to an electric motor, which brings the flywheel'srotational speed up to 4000 rev/min. (a) Find the kinetic energy stored in theflywheel.
1 J

(b) If the flywheel is to supply energy to the car as would a10.0-hp motor, find the length of time thecar could run before the flywheel would have to be brought back upto speed.
2 h (a) Find the kinetic energy stored in theflywheel.
1 J

(b) If the flywheel is to supply energy to the car as would a10.0-hp motor, find the length of time thecar could run before the flywheel would have to be brought back upto speed.
2 h

Explanation / Answer

          Diskradius is R = 1.00 m             mass ofdisk is M = 550 kg          Initial rotational speed is 1 = 0          Final  rotational speed is 2 = 4000 rev/min =4000*2 /60 rad/s = 418.66 rad/s           -----------------------------------------------------------------           The kinetic energy stored in the wheel is K =(1/2)*I*22                                                                              =-------------J                           whereI = MR2 /2 is the moment of inertia of the disk        If power of motion is P =10.0hp = 10.0*746 watt = 7460 watt        The power = work / time                       t = work / power                         = K / P                          =-------- sec To convert into hours 1hour = 3600s                                    1s = (1 /3600)h                                                      

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