Let us examine the equation for the magnitude of centripetal acceleration more practically. Consider a ball on the end of a string, being rotated about an axis. The ball experiences uniform circular motion, and is accelerated by the tension in the string, which always points toward the axis of rotation. The magnitude of the tension of the string (and therefore the acceleration of the ball) varies according to velocity and radius. If the ball is moving at a high velocity, the equation implies, a large amount of tension is required and the ball will experience a large acceleration. If the radius is very small, the equation shows, the ball will also be accelerated more rapidly.