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physics

Shear force

Shear force is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Shear force rather than just read about it. In short: In solid mechanics, shearing forces are unaligned forces acting on one part of a body in a specific direction, and another part of the body in the opposite direction. When the forces are collinear (aligned with each other), they are called tension forces or compression forces.

Shear force — main illustration
Shear force — illustration

Key takeaways

  • Shear force belongs to physics; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Shear force to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Shear force from memory before moving on to harder problems.

Reference excerpt

In solid mechanics, shearing forces are unaligned forces acting on one part of a body in a specific direction, and another part of the body in the opposite direction. When the forces are collinear (aligned with each other), they are called tension forces or compression forces. Shear force can also be defined in terms of planes: "If a plane is passed through a body, a force acting along this plane is called a shear force or shearing force."

Force required to shear steel This section calculates the force required to cut a piece of material with a shearing action. The relevant information is the area of the material being sheared, i.e. the area across which the shearing action takes place, and the shear strength of the material. A round bar of steel is used as an example. The shear strength is calculated from the tensile strength using a factor which relates the two strengths. In this case 0.6 applies to the example steel, known as EN8 bright, although it can vary from 0.58 to 0.62 depending on application. EN8 bright has a tensile strength of 800 MPa and mild steel, for comparison, has a tensile strength of 400 MPa. To calculate the force to shear a 25 mm diameter bar of EN8 bright steel;

area of the bar in mm2 = (12.52)(π) ≈ 490.8 mm2 0.8 kN/mm2 × 490.8 mm2 = 392.64 kN ≈ 40 tonne-force 40 tonne-force × 0.6 (to change force from tensile to shear) = 24 tonne-force When working with a riveted or tensioned bolted joint, the strength comes from friction between the materials bolted together. Bolts are correctly torqued to maintain the friction. The shear force only becomes relevant when the bolts are not torqued. A bolt with property class 12.9 has a tensile strength of 1200 MPa (1 MPa = 1 N/mm2) or 1.2 kN/mm2 and the yield strength is 0.90 times tensile strength, 1080 MPa in this case. A bolt with property class 4.6 has a tensile strength of 400 MPa (1 MPa = 1 N/mm2) or 0.4 kN/mm2 and yield strength is 0.60 times tensile strength, 240 MPa in this case.

See also ASTM F568M, mechanical properties of different grades of steel fasteners Cantilever method Résal effect Newton's laws of motion § Newton's third law

References

Illustrations

Shear force: Shearing forces act in one direction at the top, and the opposite direction at the bottom, causing shearing deformation.
Shearing forces act in one direction at the top, and the opposite direction at the bottom, causing shearing deformation.
Shear force: A crack or tear may develop in a body from parallel shearing forces acting in opposite directions at different points of the body. If the forces were aligned with each other, they would elongate or shorten the body, depending on their direction, rather than tear or crack it.
A crack or tear may develop in a body from parallel shearing forces acting in opposite directions at different points of the body. If the forces were aligned with each other, they would elongate or shorten the body, depending on their direction, rather than tear or crack it.

Worked examples

Example 1 — a first encounter with Shear force

Start with the simplest possible case. Write down what Shear force claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Shear force before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Shear force ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Shear force

In research
Shear force appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Shear force in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Shear force is common in secondary-school and first-year university syllabi. It links to neighbouring topics Civil engineering, Force, so understanding it makes those chapters shorter.
In everyday life
Look for Shear force outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Shear force in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Shear force means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Shear force out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Shear force in simple terms?

In solid mechanics, shearing forces are unaligned forces acting on one part of a body in a specific direction, and another part of the body in the opposite direction. When the forces are collinear (aligned with each other), they are called tension forces or compression forces.

Why does Shear force matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Shear force?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Shear force.

Tags

  • Civil engineering
  • Force

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