What should a person do to reduce his (angular) speed on a freely rotating platform?

To reduce his angular speed on a freely rotating platform, a person should spread his hands outwards; option [C]. This action increases the person’s moment of inertia. According to the principle of conservation of angular momentum, when no external torque acts on a system, the angular momentum remains constant. Angular momentum is the product of moment of inertia and angular velocity. By spreading the hands outwards, the moment of inertia increases. Since angular momentum must be conserved, an increase in moment of inertia results in a decrease in angular velocity, thereby reducing the person’s rotational speed.

This phenomenon is similar to a figure skater extending their arms to slow down during a spin. The principle is used in various applications where control of rotational speed is required. Therefore, to effectively reduce angular speed on a freely rotating platform, one should choose option [C] Spread your hands outwards. This approach leverages fundamental principles of physics to achieve the desired reduction in speed.