It has been proposed to build flywheels into cars, which could spin with very high angular velocity. When a car stops at a stop sign some of the car's kinetic energy is diverted into the kinetic energy of the rotating wheel, instead of all into heat energy in the brakes. Then the wheel's energy will be used to help propel the car up to speed again. The proposal is to mount the wheel horizontally, so its axis is vertical, attached to the frame of the car. If there is just a single wheel, what effect would it have on the car, if any, if the car (a) turned right; (b) turned left; (c) started up a hill; (d) started down a hill? (e) What advantage might there be in mounting two counterrotating wheels on the same axle?