MCQs / Physics / Deformation of Solids

Deformation of Solids MCQs — Physics

110 multiple-choice questions on Deformation of Solids from Physics, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. A wire of length 1.5 m is extended by 0.6 mm. The strain is:

  1. 4 10^-4
  2. 2500
  3. 8 10^-4
  4. 0.4

Answer: A) 4 10^-4

Explanation: Strain = el = 6 10^-41.5 = 4 10^-4 (no unit). SLO P-11-B-24 · Application

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2. Diamond and graphite are both carbon. Diamond is hard because:

  1. it is amorphous
  2. each atom is bonded to four others in a rigid 3-D lattice
  3. it is a polymer
  4. it has free molecules

Answer: B) each atom is bonded to four others in a rigid 3-D lattice

Explanation: Strong covalent bonds in three dimensions. SLO P-11-B-22 · Understanding

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3. A spring stretched beyond its elastic limit will:

  1. return to its original length
  2. become shorter
  3. become stiffer than before
  4. be permanently longer when the load is removed

Answer: D) be permanently longer when the load is removed

Explanation: Plastic deformation. SLO P-11-B-26 · Understanding

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4. In plastic deformation, the work done on the material is mainly:

  1. converted to light
  2. stored as elastic energy and returned
  3. converted to heat (not recovered)
  4. destroyed

Answer: C) converted to heat (not recovered)

Explanation: Atoms slipping generate internal energy. SLO P-11-B-26 · Understanding

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5. The cables of a suspension bridge are mainly under:

  1. tension
  2. no stress
  3. compression
  4. torsion

Answer: A) tension

Explanation: They are stretched by the load. SLO P-11-B-23 · Understanding

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6. If the extension of a spring is doubled (within Hooke's law), the work done becomes:

  1. 4 times as large
  2. half
  3. 2 times as large
  4. unchanged

Answer: A) 4 times as large

Explanation: W = 12ke^2. SLO P-11-B-27 · Application

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7. If the diameter reading is 2% too large, the calculated Young modulus will be:

  1. about 4% too small
  2. unchanged
  3. 2% too large
  4. 4% too large

Answer: A) about 4% too small

Explanation: Y propto 1/d^2. SLO P-11-B-25 · Understanding

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8. The area under a stress–strain graph represents:

  1. the Young modulus
  2. energy stored per unit volume
  3. the force
  4. total work done

Answer: B) energy stored per unit volume

Explanation: Stress × strain has units J/m^3. SLO P-11-B-27 · Application

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9. Hooke's law states that, up to the limit of proportionality:

  1. stress equals strain
  2. extension is directly proportional to the applied force
  3. extension is inversely proportional to force
  4. force is constant

Answer: B) extension is directly proportional to the applied force

Explanation: F = ke. SLO P-11-B-26 · Understanding

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10. A wire of length 2 m and cross-section 1 10^-6 m^2 extends by 2 mm under 200 N. The Young modulus is:

  1. 2 10^10 Pa
  2. 2 10^12 Pa
  3. 2 10^11 Pa
  4. 4 10^11 Pa

Answer: C) 2 10^11 Pa

Explanation: Y = F/Ae/l = FlAe = 2 10^11 Pa. SLO P-11-B-24 · Application

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11. A crystalline solid has:

  1. a range of softening temperatures
  2. a sharp melting point
  3. the same properties as a gas
  4. no melting point

Answer: B) a sharp melting point

Explanation: All bonds are equivalent, so they break at one temperature. SLO P-11-B-22 · Understanding

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12. Glass is sometimes called a 'supercooled liquid' because:

  1. it has a crystal lattice
  2. its disordered structure resembles a liquid's frozen in place
  3. it is a liquid below 0 °C
  4. it flows quickly at room temperature

Answer: B) its disordered structure resembles a liquid's frozen in place

Explanation: It has short-range order only, like a liquid. SLO P-11-B-22 · Understanding

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13. A wire (Y = 2 10^11 Pa) of length 2 m and area 1 10^-6 m^2 carries 100 N. Its extension is:

  1. 2 mm
  2. 1 mm
  3. 10 mm
  4. 0.1 mm

Answer: B) 1 mm

Explanation: e = FlYA = 0.001 m = 1 mm. SLO P-11-B-24 · Application

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14. In a crystalline solid, the atoms are arranged:

  1. in a regular, repeating three-dimensional pattern
  2. in long tangled chains only
  3. as in a liquid
  4. randomly with no order

Answer: A) in a regular, repeating three-dimensional pattern

Explanation: This long-range order is called a lattice. SLO P-11-B-22 · Understanding

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15. A spring of constant 100 N/m stores 0.5 J of elastic energy. Its extension is:

  1. 0.05 m
  2. 0.2 m
  3. 0.01 m
  4. 0.1 m

Answer: D) 0.1 m

Explanation: x = 2Ek = 2(0.5)100 = 0.1 m. SLO P-11-B-28 · Application

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16. Compressive forces on a rod act:

  1. inward along its length, pushing the ends together
  2. outward, pulling the ends apart
  3. perpendicular to the rod
  4. only at one end

Answer: A) inward along its length, pushing the ends together

Explanation: Two equal and opposite inward forces. SLO P-11-B-23 · Understanding

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17. A graph of load F against extension e is a straight line of gradient k. The Young modulus is:

  1. Y = kAl
  2. Y = kAl
  3. Y = klA
  4. Y = kAl

Answer: C) Y = klA

Explanation: Y = FlAe = lA Fe. SLO P-11-B-25 · Understanding

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18. A wire of length 2 m is extended by 1 mm. The strain is:

  1. 0.5
  2. 0.001
  3. 5 10^-4
  4. 2000

Answer: C) 5 10^-4

Explanation: Strain = el = 0.0012 = 5 10^-4 (no unit). SLO P-11-B-24 · Application

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19. A wire of diameter 0.5 mm carries a load of 500 N. The stress in the wire is:

  1. 5.09 10^9 Pa
  2. 1.02 10^10 Pa
  3. 2.55 10^9 Pa
  4. 6.37 10^8 Pa

Answer: C) 2.55 10^9 Pa

Explanation: A = pi r^2 = pi(2.5 10^-4)^2 = 1.96 10^-7 m^2; sigma = F/A = 2.55 10^9 Pa. SLO P-11-B-24 · Application

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20. Strain has:

  1. no unit (it is a ratio of lengths)
  2. the unit m
  3. the unit N/m^2
  4. the unit N

Answer: A) no unit (it is a ratio of lengths)

Explanation: varepsilon = e/l. SLO P-11-B-24 · Application

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21. Which is a polymeric solid?

  1. copper
  2. rubber
  3. diamond
  4. sodium chloride

Answer: B) rubber

Explanation: Rubber consists of long, cross-linked chains. SLO P-11-B-22 · Understanding

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22. The ultimate tensile stress (UTS) is:

  1. the stress at zero strain
  2. the elastic limit
  3. the maximum stress a material can withstand before breaking
  4. the Young modulus

Answer: C) the maximum stress a material can withstand before breaking

Explanation: The highest point on the stress–strain curve. SLO P-11-B-26 · Understanding

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23. A spring of spring constant 100 N/m is stretched by 0.1 m (within the limit of proportionality). The elastic potential energy stored is:

  1. 1 J
  2. 5 J
  3. 0.25 J
  4. 0.5 J

Answer: D) 0.5 J

Explanation: Ep = 12kx^2 = 12(100)(0.1)^2 = 0.5 J. SLO P-11-B-28 · Application

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24. The formula Ep = 12kx^2 applies only when:

  1. the deformation is plastic
  2. the material has broken
  3. the material obeys Hooke's law (within the limit of proportionality)
  4. the force is zero

Answer: C) the material obeys Hooke's law (within the limit of proportionality)

Explanation: It comes from a straight-line graph. SLO P-11-B-28 · Application

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25. A spring with k = 200 N/m is stretched 0.1 m. The area under its force–extension graph is:

  1. 10 J
  2. 20 J
  3. 1 J
  4. 2 J

Answer: C) 1 J

Explanation: 12(200)(0.1)^2 = 1 J. SLO P-11-B-27 · Application

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