The answer is : Gravity draws an object towards its strongest point. The main things holding you back are air resistance and friction. As a hill gets steeper, you are more in line with the center of gravity, so it overcomes friction and you move faster. Eventually when you are moving vertically there is no friction other than air resistance itself. At this time you will accelerate at 32 feet per second every second until you either hit something or reach terminal velocity which is around 120 mph. Air resistance (on the Earth at least) will not allow you to travel any faster. Hope this Helped! Good Luck! :)
