People in a revolving restaurant on the Seattle Space Needle. People in a regular restaurant. People at a bus stop. In a good swivel chair you must push against something to start or stop spinning. Moment of inertia.
Ice skaters pull their arms in to speed up.
Applies a torque. Causes a linear acceleration. Decreases the moment of inertia. A crackpot inventor friend shows you a bicycle that uses the entire back tire as the rear sprocket, instead of just a small sprocket near the hub. The pedals would require more force, but it would go faster.