When a stone is thrown into the air it's surface will be in contact with the surrounding air. Analyse the stresses existing between the stone and the surrounding air.
The collisions of the stone with air molecules tend to slow the stone down slightly. A frictional force called drag is exerted upon the stone. It is of two types: (1) pressure drag (higher pressure in front that behind) and (2) boundary layer friction along the sides.
To analyze the stresses existing between the stone and the surrounding air when it is thrown into the air, we need to consider the concepts of fluid dynamics.
When the stone is thrown into the air, it experiences a force of gravity pulling it downward, while also having an initial upward velocity. As it moves upward, it interacts with the surrounding air, which has viscosity, density, and pressure.
The interaction between the stone and the air gives rise to two main stresses: aerodynamic drag and buoyancy.
1. Aerodynamic drag: As the stone moves through the air, it experiences resistance, known as aerodynamic drag. This drag force depends on the shape and velocity of the stone and the properties of the surrounding air. The drag force acts opposite to the direction of motion, slowing down the stone. The difference in velocity and pressure between the stone and the air causes this resistance.
2. Buoyancy: The stone in the air also experiences buoyancy, similar to the buoyant force acting on submerged objects in a fluid. Buoyancy is caused by the displacement of air by the stone. The stone displaces a volume of air equal to its volume, and the resulting buoyant force pushes it upward. If the density of the stone is greater than that of the surrounding air, it will experience a net downward force due to gravity. On the other hand, if the density of the stone is less than that of the air, it will experience a net upward force due to buoyancy.
Therefore, the interaction between the stone and the surrounding air creates both aerodynamic drag and buoyancy forces, which can significantly affect the stone's motion while it is in the air. These forces depend on factors such as the stone's shape, velocity, density, and the properties of the surrounding air.