Final answer:
The statement is true; rotation is different from rolling, as exemplified by a diver's body movements to increase or decrease angular velocity while maintaining angular momentum.
Step-by-step explanation:
The statement that rotation is different from rolling, in the context of a swimmer going from being on their front to their back or vice versa, is true. When a competitive diver pulls their limbs in and curls up their body to perform flips, which is a rotation, their angular velocity increases due to conservation of angular momentum. By bringing their mass closer to the axis of rotation, they reduce their moment of inertia, allowing for a faster spin. Prior to entering the water, extending their limbs decreases their angular velocity because their moment of inertia increases, but their angular momentum remains constant. This is an example of the principle of conservation of angular momentum, where the product of moment of inertia and angular velocity remains the same in the absence of external torques. Extending limbs also helps divers to enter the water smoothly, minimizing resistance and preventing a painful belly flop.