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Exam level15 past questions

Mechanical properties of solids

Study of how solids respond to applied forces, including stress, strain, elastic moduli (Young's modulus, bulk modulus), and breaking stress.

Why this shows up in the exam

NEET tests your understanding of how materials deform and break under various forces, including calculations and conceptual reasoning.

How NEET tests this

Application · 11 QsStatement analysis · 3 QsDirect recall · 3 Qs

Learn the idea

Mechanical properties of solids describe how a solid body deforms under applied forces; the key insight is that stress (force per unit area) and strain (relative deformation) are linked by a material‑specific constant – the elastic modulus.

🧠 Memory hook: Think of a solid as a tightly‑packed crowd: the tighter the crowd (strong inter‑atomic coupling), the harder it is to squeeze – just like a low compressibility.

Get this one clearly and it pays off every single time it shows up in the paper. 🎯

Formulas & facts to keep ready

  • Stress σ = Force F / Cross‑sectional area A (N m⁻²)
  • Strain ε = Extension ΔL / Original length L (dimensionless)
  • Young's modulus Y = σ / ε = (F L) / (A ΔL) (N m⁻²)
  • Bulk modulus K = -ΔP / (ΔV/V) = reciprocal of compressibility (N m⁻²)
  • Breaking stress = maximum σ a material can sustain before rupture
  • For a given material Y is independent of its dimensions; only geometry (A, L) influences ΔL

How to approach it

  1. 1Read the question and list what is given – force, length, area, material, or breaking condition
  2. 2Write the appropriate relation: σ = F/A, ε = ΔL/L, or Y = σ/ε
  3. 3Replace σ or ε with F, A, L, ΔL using Y (or K) and solve for the unknown
  4. 4Check units and whether the answer should be a comparison, ratio or numerical value

Worked example — watch it click

Assertion A: The compressibility of solids is less than that of gases and liquids. Reason R: There is tight coupling between the neighbouring atoms in solids.

  • ✅If both assertion and reason are true, and reason is the correct explanation of assertion.
  • B)If both assertion and reason are true, but reason is not the correct explanation of assertion.
  • C)If assertion is true, but reason is false.
  • D)If both assertion and reason are false.

The concept behind this problem

The assertion‑reason pair tests the link between bulk modulus (compressibility) and the microscopic picture of atoms being tightly bound in solids, which is exactly what the concept of mechanical properties of solids emphasizes.

Step by step

  1. 1Assertion A is true: Compressibility is the reciprocal of bulk modulus (K).
  2. 2Solids have very high bulk moduli (K ≈ 10¹⁰-10¹¹ Pa), liquids have moderate values (K ≈ 10⁹ Pa), and gases have very low values (K ≈ 10⁵ Pa at atmospheric pressure).
  3. 3Therefore, compressibility of solids << liquids << gases.
  4. 4Reason R is true: In solids, atoms are tightly coupled with strong interatomic forces and small equilibrium separations, making them highly resistant to volume change.
  5. 5This tight coupling is the fundamental reason for low compressibility.
  6. 6The reason correctly explains the assertion.

Watch out

Students often answer that the reason is false, overlooking that tight atomic coupling is precisely why solids have a very low compressibility.

Common slip-ups that cost marks

  • •Confusing stress with pressure – both have same units but pressure acts on fluids, stress on solids
  • •Using radius directly instead of area (A = πr²) when applying formulas
  • •Mixing up Young's modulus (tensile) with bulk modulus (volumetric) in a single calculation

🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.

Practise it

These are real questions from past NEET papers that test this exact idea.

Question 1 of 15NEET 2014

The following four wires are made of the same material. Which of these will have the largest extension when the same tension is applied?

Push further

More challenging

12 harder questions built from the past papers above — a step up in difficulty, with distractors designed so you can't get there by elimination. Written and checked by our reviewers, not from a real paper.

Question 1 of 12

Assertion A: Gases are highly compressible. Reason R: The intermolecular forces in gases are negligible, and molecules are far apart.

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