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Deformation of Solids MCQs — Physics (page 3)

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.

51. Metals are generally:

  1. polycrystalline (many small crystals called grains)
  2. polymeric
  3. liquids
  4. amorphous

Answer: A) polycrystalline (many small crystals called grains)

Explanation: Each grain is a tiny crystal. SLO P-11-B-22 · Understanding

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52. The gradient of a stress–strain graph in the linear region gives:

  1. the elastic potential energy
  2. the Young modulus
  3. the extension
  4. the breaking stress

Answer: B) the Young modulus

Explanation: Y = sigma/varepsilon. SLO P-11-B-25 · Understanding

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53. Elastic deformation is deformation in which the material:

  1. stays permanently deformed
  2. returns to its original shape when the force is removed
  3. breaks
  4. melts

Answer: B) returns to its original shape when the force is removed

Explanation: e.g. a spring under a small load. SLO P-11-B-26 · Understanding

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54. On a load–extension graph, the limit of proportionality is where:

  1. the graph starts
  2. the graph stops being a straight line
  3. the extension is zero
  4. the wire breaks

Answer: B) the graph stops being a straight line

Explanation: Hooke's law stops applying. SLO P-11-B-26 · Understanding

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55. When a wire is stretched, the distance between its atoms:

  1. increases slightly
  2. stays the same
  3. decreases
  4. becomes zero

Answer: A) increases slightly

Explanation: Attractive forces pull back. SLO P-11-B-23 · Understanding

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56. A wire of diameter 2 mm carries a load of 200 N. The stress in the wire is:

  1. 6.37 10^7 Pa
  2. 1.27 10^8 Pa
  3. 1.59 10^7 Pa
  4. 2.55 10^8 Pa

Answer: A) 6.37 10^7 Pa

Explanation: A = pi r^2 = pi(0.001)^2 = 3.14 10^-6 m^2; sigma = F/A = 6.37 10^7 Pa. SLO P-11-B-24 · Application

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57. A car's crumple zone is designed to undergo:

  1. no deformation
  2. brittle fracture
  3. elastic deformation only
  4. plastic deformation, absorbing energy

Answer: D) plastic deformation, absorbing energy

Explanation: Permanent deformation absorbs kinetic energy. SLO P-11-B-26 · Understanding

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58. Readings are taken while loading and unloading to:

  1. check the wire stays within its elastic limit
  2. measure the diameter
  3. save time
  4. increase the extension

Answer: A) check the wire stays within its elastic limit

Explanation: Readings should agree if deformation is elastic. SLO P-11-B-25 · Understanding

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59. The original length of the wire is measured with:

  1. a spring balance
  2. a metre rule (or tape)
  3. a stopwatch
  4. a micrometer

Answer: B) a metre rule (or tape)

Explanation: It is long (≈ 2 m). SLO P-11-B-25 · Understanding

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60. A spring obeying Hooke's law extends 2 cm under a final force of 40 N. The work done in stretching it is:

  1. 0.4 J
  2. 0.8 J
  3. 0.2 J
  4. 40 J

Answer: A) 0.4 J

Explanation: Work = area of the triangle = 12Fe = 12(40)(0.02) = 0.4 J. SLO P-11-B-27 · Application

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61. A safety precaution in the Young modulus experiment is to:

  1. wear goggles and keep feet away from the falling loads
  2. use very short wires
  3. use a ruler to measure extension
  4. heat the wire

Answer: A) wear goggles and keep feet away from the falling loads

Explanation: A breaking wire can whip and loads can fall. SLO P-11-B-25 · Understanding

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62. A substance that cools too quickly for its atoms to arrange in order forms:

  1. a glassy (amorphous) solid
  2. a polymer
  3. a perfect crystal
  4. a gas

Answer: A) a glassy (amorphous) solid

Explanation: Rapid cooling 'freezes' the disorder. SLO P-11-B-22 · Understanding

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63. Beyond the yield point, a ductile metal wire:

  1. returns to its original length
  2. stretches a lot for little extra load (plastic flow)
  3. becomes brittle
  4. contracts

Answer: B) stretches a lot for little extra load (plastic flow)

Explanation: Layers of atoms slip past each other. SLO P-11-B-26 · Understanding

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64. A long, thin wire is used because:

  1. it doesn't stretch
  2. it gives a larger, more measurable extension
  3. it is cheaper
  4. it reduces the load needed to break it

Answer: B) it gives a larger, more measurable extension

Explanation: e = FlYA: large l, small A give large e. SLO P-11-B-25 · Understanding

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65. The Young modulus is:

  1. strain divided by stress
  2. tensile stress divided by tensile strain
  3. force divided by extension
  4. stress × strain

Answer: B) tensile stress divided by tensile strain

Explanation: Y = sigma/varepsilon. SLO P-11-B-24 · Application

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66. The Young modulus of a material depends on:

  1. the wire's diameter
  2. the wire's length
  3. the load applied
  4. the material only, not the wire's dimensions

Answer: D) the material only, not the wire's dimensions

Explanation: It is a property of the material. SLO P-11-B-24 · Application

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67. A beam that bends has:

  1. one side in tension and the other in compression
  2. only compression
  3. no stress at all
  4. only tension

Answer: A) one side in tension and the other in compression

Explanation: The outside of the bend stretches and the inside squashes. SLO P-11-B-23 · Understanding

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68. A spring of constant 200 N/m stores 9 J of elastic energy. Its extension is:

  1. 0.3 m
  2. 0.09 m
  3. 0.15 m
  4. 0.6 m

Answer: A) 0.3 m

Explanation: x = 2Ek = 2(9)200 = 0.3 m. SLO P-11-B-28 · Application

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69. A deforming force always produces in the solid:

  1. a loss of mass
  2. a magnetic field
  3. an increase in temperature only
  4. an internal restoring force opposing the deformation

Answer: D) an internal restoring force opposing the deformation

Explanation: Intermolecular forces resist being stretched or squashed. SLO P-11-B-23 · Understanding

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70. The gradient of a force–extension graph (straight line) gives:

  1. the work done
  2. the stress
  3. the spring constant k
  4. the elastic energy

Answer: C) the spring constant k

Explanation: k = F/e. SLO P-11-B-27 · Application

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71. A wire of diameter 0.8 mm carries a load of 50 N. The stress in the wire is:

  1. 3.98 10^8 Pa
  2. 9.95 10^7 Pa
  3. 2.49 10^7 Pa
  4. 1.99 10^8 Pa

Answer: B) 9.95 10^7 Pa

Explanation: A = pi r^2 = pi(4 10^-4)^2 = 5.03 10^-7 m^2; sigma = F/A = 9.95 10^7 Pa. SLO P-11-B-24 · Application

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72. Deformation of a solid means:

  1. a change in its colour
  2. a change in its mass
  3. a change in its shape or size caused by a force
  4. melting of the solid

Answer: C) a change in its shape or size caused by a force

Explanation: Forces stretch, compress, bend or twist solids. SLO P-11-B-23 · Understanding

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73. A spring obeying Hooke's law extends 5 cm under a final force of 100 N. The work done in stretching it is:

  1. 250 J
  2. 5 J
  3. 1.25 J
  4. 2.5 J

Answer: D) 2.5 J

Explanation: Work = area of the triangle = 12Fe = 12(100)(0.05) = 2.5 J. SLO P-11-B-27 · Application

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74. The legs of a table supporting a heavy load are under:

  1. compression
  2. tension
  3. shear only
  4. torsion

Answer: A) compression

Explanation: The load pushes down; the floor pushes up. SLO P-11-B-23 · Understanding

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75. A material with a high Young modulus is:

  1. stiff
  2. brittle by definition
  3. plastic
  4. very stretchy

Answer: A) stiff

Explanation: A large stress gives only a small strain. SLO P-11-B-26 · Understanding

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