Hi all, In the attached image I have a cylinder shaped wheel with a air pocket embedded near its edge. The wheel has the same density as water and is fully submerged in a tank of water. Also the wheel is only free to spin about its center axis. If the wheel is rotated down the air pocket will cause the wheel to spin upward but how? Buoyancy is defined as an upward acting force, caused by fluid pressure. The wheel is under pressure from all side with a greater pressure from the bottom caused by gravity but I'm not understanding how fluid pressure can cause the wheel to spin upward? If a ping pong ball is fully submerged in a tank of water the water is able to flow under the ball to give it lift. but in this wheel example the wheel is not lifting but spinning so water is not flowing at all. Maybe someone could help me understand this a little better. Thanks!