Batteries are used in todays hybrid cars to capture the wasted energy of downhill and braking energy. Engineers have been looking at using 2 oppositely spinning flywheels , positioned under the car. If each flywheel is a disk of steel r = .9 meters and thickness of 10 cm, iron density = 8 grams per cc, and the maximum spin rate is 10,000 rpm, how much energy could this system store? Ek=__________joules. How many gallons of gas is this equivalent to? ________ gal.