37. The longer the radius of rotation the greater the centrifugal force with the same angular velocity and weight.

Activity applied to this principle: Gymnastics giant swing on the horizontal bar.

Explanation:

In the figure above, notice that the radius of rotation is basically the same 360 degrees around the bar. Because of this the centrifugal force will remain constant. However, in performing, the reaction to resistive torque produced by gravity would make it difficult to maintain this position as the gymnast proceeds around the bar.

In the illustration shown below, notice that just after passing the bottom point of the swing, the gymnast flexes in two places, the hips and the elbows, while allowing the shoulder joint to extend from a fully flexed position overhead to midposition in front of the body. These actions bring the mass closer to the bar (reducing the body's radius of rotation) and thus tend to counteract the reduction in the body's angular momentum during the upswing. By bringing the center of gravity (not to be confused with the radius of rotation) closer to the bar on the upswing, the gymnast also decreases the force arm of the gravitational force and thus decreases the magnitude of its resistive torque. The reduction of the resistive torque produced by gravity allows the body to maintain its angular velocity for a longer period of time, and, consequently, as one approaches the top of the bar, he moves faster than he would have had he remained in the rigid position as in the illustration above.