Before we understand what is shear force in Fluid, we must understand what is shear force, and definitions with some good and basic examples to get clear with the concept.

What is shear force?

Shear force is an internal force that acts parallel to the surface or cross-section of a material, caused by external forces or loads trying to slide one part of the material relative to another.

Imagine you have a big sandwich with lots of layers, like bread, cheese, lettuce, and tomato. Now, if you hold the sandwich with both hands and push one hand up and the other hand down, the layers might start to slide past each other. That sliding feeling between the layers is kind of like what happens with shear force.

Shear force happens when something pushes or pulls on a material in a way that tries to make one part slide against another part, just like with your sandwich

Also Read: What is Stress strain Curve

What is shear force in engineering?

‘In engineering, shear force refers to an internal force within a structure or material that occurs when external loads or forces try to slide one part of the material parallel to another. It acts along the cross-sectional plane of a structure, as opposed to normal force, which acts perpendicular to the plane.

Example:

Imagine a horizontal beam supported at both ends. If a vertical load is applied in the middle, the beam experiences:

• Shear forces near the supports where the beam “pushes back” to counteract the load.
• These forces try to slide the material layers within the beam relative to one another.

Importance of shear force in Engineering:

Shear force is critical when designing structures like bridges, buildings, or machine parts. Engineers calculate shear forces to:

• Ensure the material can withstand these forces without failing.
• Prevent issues like cracks or deformation that could weaken the structure.

Visualization:

Think of cutting paper with scissors. The blades apply shear force to the paper, causing it to split along the line of force. In structures, shear force similarly tries to “cut” the material internally.

What is shear force in fluid?

In fluids, shear force is the force that acts parallel to the surface of a fluid layer due to the fluid’s viscosity (its internal “stickiness”). It occurs when adjacent layers of a fluid move at different speeds, creating a sliding or shearing motion between the layers.

Example:

Imagine water flowing through a pipe. The water touching the pipe walls moves slowly because of friction, while the water in the middle flows faster. The difference in speed between these layers creates shear forces within the fluid.

Shear Stress:

Shear force in a fluid is often described in terms of shear stress (τ\tauτ), which is the force per unit area. It’s given by the formula:τ=μdudy\tau = \mu \frac{du}{dy}τ=μdydu​

Where:

• μ\muμ = viscosity of the fluid (how thick or sticky it is)
• dudy\frac{du}{dy}dydu​ = rate of change of velocity between layers (velocity gradient)

Importance:

• Engineering: Helps design systems like pipelines, turbines, and aircraft to account for fluid resistance.
• Everyday Life: Explains why honey flows more slowly than water—it has a higher viscosity, so it resists shear forces more.

What is shear force in physics

In physics, shear force is a type of force that acts parallel to a surface or plane within a material. It arises when external forces try to make one part of an object slide or deform relative to another part. Unlike normal forces, which act perpendicular to a surface, shear forces act tangentially (along the surface).

Simple Explanation:

Imagine you’re holding a deck of cards. If you push the top of the deck sideways while keeping the bottom still, the layers of cards slide against each other. This sliding effect is caused by a shear force.

In Solid Materials:

Shear force occurs when an object experiences stress that tries to distort its shape. For example:

• In a beam supported at both ends, a vertical load causes shear forces near the supports.
• The material resists this by developing internal shear forces to maintain its structure.

In Fluids:

Shear force is associated with viscosity and occurs when layers of fluid move at different speeds. For example:

• Water flowing through a pipe creates shear force between layers moving at different velocities.

Key Importance in Physics:

• Helps in understanding material deformation and failure.
• Essential in designing structures, vehicles, and machinery to ensure stability and safety.
• Crucial for analyzing fluid dynamics in various applications like aerodynamics or hydraulics.