Q: A diver can turn several somersaults before striking water , Explain .
Sol: Let us consider the diver as a system and his limbs as its components . When he leaves the diving board , he has a certain angular speed ωo about the horizontal axis through his centre of mass . Now there are no external forces acting on him except gravity and gravity exerts no torque about his centre of mass . His angular momentum remains constant and Io ωo = I ω . When he pulls in his limbs , his moment of inertia decreases and consequently his angular velocity increases .