To drive a typical car at 40 mph on a level road for one hour requires about 3.2 × 10⁷ J of energy. Suppose one tried to store this much energy in a spinning solid cylindrical flywheel which was then coupled to the wheels of the car. A large flywheel cannot be spun too fast or it will fracture. If one used a flywheel of radius 0.60 m and mass 400 kg, what angular speed would be required to store 3.2 ×10⁷ J (Incidentally, 2500 rpm is about the maximum feasible rate of revolution with present materials technology for such a flywheel.)

a. 943 rad/s

b. 530 rad/s

c. 1800 rad/s

d. 3620 rad/s

e. 5470 rad/s