Centripetal force: the coaster enters a banked curve, and as the track is curved and as the car is in a state of acceleration, it becomes subject to centripetal force, which may give the riders the sensation of being pushed sideways. But if the track is banked at the correct angle for the speed, the force the riders feel push them into their seats. Banking the turn converts the lateral g-forces the riders feel into positive g-forces, as pressure is felt from the floor as well as from the side of the car.
If the speed of the coaster doubles, centripetal forces quadruple, unless the radius of the curve is also quadrupled. As a result, shallower curves are found on larger, faster coasters than on smaller ones. Centrifugal force can be increased by increasing either (1) the speed of rotation, (2) the mass of the body, or (3) the radius, which is the distance of the body from the center of the curve. Increasing either the mass or the radius increases the centrifugal force proportionally, but increasing the speed of rotation increases it in proportion to the square of the speed; that is, an increase in speed of 10 times, say from 10 to 100 revolutions per minute, increases the centrifugal force by a factor of 100. Centrifugal force is expressed as a multiple of g, the symbol for normal gravitational force (strictly speaking, the acceleration due to gravity).