a roller-coaster car rolls down a frictionless track, reaching speed v0v0 at the bottom. if you want the car to go twice as fast at the bottom, by what factor must you increase the height of the track? a roller-coaster car rolls down a frictionless track, reaching speed at the bottom. if you want the car to go twice as fast at the bottom, by what factor must you increase the height of the track? you must increase the track he