The Gravitron single-car roller coaster consists of a singleloop-the-loop. The car is initially pushed, giving it just theright mechanical energy so the riders on the coaster will feel"weightless" when they pass through the top of the circular arc. How heavy will they feel when they pass through the bottom of thearc (that is, what is the normal force pressing up on them whenthey are at the bottom of the loop)? Express the answer as amultiple of mg (their actual weight). Assume any effectsof friction or of air resistance are negligible.