Forces on a Surface A force on a surface is any interaction force that acts on the surface itself, rather than on a fluid particle within the surface. This...
Forces on a Surface
A force on a surface is any interaction force that acts on the surface itself, rather than on a fluid particle within the surface. This includes the normal force (pushing inward), the shear force (pushing outward), and the gravitational force (pulling downwards).
Normal Force
The normal force is the force that acts perpendicular to the surface, preventing the surface from being pushed or pulled apart. It is the force that allows a book to sit on a table, for example.
Shear Force
The shear force is the force that acts parallel to the surface, causing the surface to deform. It is the force that causes water to flow down a drain, for example.
Gravitational Force
The gravitational force is the force that pulls objects with mass towards each other. It is the force that keeps the Earth in orbit around the Sun, for example.
The net force acting on a surface is equal to the resultant force, which is the vector sum of all the individual forces. The resultant force can cause the surface to deform, move, or even break.
Examples
When you walk on the floor, the normal force pushes you down, and the shear force prevents you from slipping.
When you pour water down a drain, the shear force causes the water to flow.
The gravitational force is responsible for the Earth's rotation.
Understanding the forces on a surface is important for understanding many aspects of fluid dynamics, such as fluid flow, pressure, and equilibrium