Lesson 4.2.1

4.2.1 Hooke's law and force-extension graphs Quiz: Pearson Edexcel Physics, Unit 4

20 questions

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Lesson 4.2.1, Hooke's law and force-extension graphs: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 4: Materials, written with Revision Ninja.

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The 20 questions

  1. What does Hooke's law state?

    • Extension is independent of the applied force for all materials
    • Extension is directly proportional to the applied force, provided the limit of proportionality is not exceeded
    • Force is inversely proportional to the extension
    • Force is proportional to the square of the extension at all times

  2. What is the SI unit of the stiffness k of a spring?

    • N/m
    • N m
    • kg m^-1
    • N m^-2

  3. In the linear region of a force-extension graph, what does the gradient represent?

    • The Young modulus of the material
    • The stress in the material
    • The elastic strain energy stored
    • The stiffness of the object

  4. What happens to a force-extension graph beyond the limit of proportionality?

    • It returns to the origin with no residual extension
    • It remains straight but with a smaller gradient
    • It becomes a horizontal line
    • It is no longer a straight line through the origin

  5. What is meant by plastic deformation?

    • The material returns to its original length when the load is removed
    • The material does not return to its original length after the load is removed
    • The material extends linearly for any force applied
    • The material becomes permanently stiffer after being stretched

  6. What is the yield point of a material on a force-extension graph?

    • The point at which the material breaks
    • The point at which extension increases rapidly with little or no increase in force
    • The point at which the stiffness reaches its maximum
    • The point at which the material first becomes elastic

  7. What is the elastic limit of a material?

    • The point where Hooke's law stops being valid for a spring
    • The point where the force-extension graph is a straight line through the origin
    • The point beyond which the material undergoes permanent deformation when the load is removed
    • The point where the material first breaks under load

  8. A spring of stiffness 40 N/m is extended by 0.25 m. What force is needed?

    • 160 N
    • 0.16 N
    • 10 N
    • 4.0 N

  9. A force of 6.0 N produces an extension of 0.12 m in a spring obeying Hooke's law. What is its stiffness?

    • 0.02 N/m
    • 5.0 N/m
    • 50 N/m
    • 0.72 N/m

  10. A spring of stiffness 200 N/m is pulled with a force of 3.0 N. What is its extension?

    • 15 mm
    • 0.67 mm
    • 1.5 mm
    • 600 mm

  11. Spring X has stiffness 20 N/m and spring Y has stiffness 60 N/m. The same force is applied to each. How do their extensions compare?

    • Both extend by the same amount
    • X extends three times as far as Y
    • X extends nine times as far as Y
    • Y extends three times as far as X

  12. A spring of stiffness 150 N/m is stretched from its natural length to an extension of 0.040 m. What force is needed?

    • 150 N
    • 6.0 N
    • 0.27 N
    • 3.75 N

  13. As the force on a wire increases from 2.0 N to 5.0 N, its extension increases from 0.040 m to 0.100 m. What is its stiffness in this region?

    • 50 N/m
    • 70 N/m
    • 30 N/m
    • 0.012 N/m

  14. A spring of stiffness 400 N/m is compressed by 0.030 m. What force is needed to hold it compressed?

    • 12 N
    • 13 N
    • 1200 N
    • 0.13 N

  15. A 0.50 kg mass hangs on a spring and produces an extension of 0.196 m. Take g = 9.8 N/kg. What is the stiffness of the spring?

    • 250 N/m
    • 5.0 N/m
    • 2.5 N/m
    • 25 N/m

  16. A force-extension graph is straight up to a point and then curves so that extension grows rapidly for little extra force. What is the most likely explanation?

    • The Hooke's law constant of the wire has increased
    • The material has passed its yield point and is deforming plastically
    • The wire has become stiffer as it was stretched
    • The wire has returned to its original length

  17. A 0.40 kg mass hangs at equilibrium from a spring of stiffness 60 N/m. Take g = 9.8 N/kg. What is the extension of the spring?

    • 0.065 m
    • 0.41 m
    • 0.15 m
    • 0.0065 m

  18. A student plots force against the total length of a spring rather than its extension. Which statement is correct?

    • The line passes through the origin, so its gradient is zero
    • The line is curved because length is never proportional to force
    • The line is straight with gradient k, but it does not pass through the origin because the spring has a natural length
    • The gradient gives the Young modulus rather than the stiffness

  19. A spring obeys Hooke's law. A force of 3.0 N gives an extension of 0.060 m, and a force of 9.0 N gives an extension of 0.20 m. What is its stiffness?

    • 30 N/m
    • 50 N/m
    • 43 N/m
    • 67 N/m

  20. Why is the force-extension graph of a spring a straight line up to the limit of proportionality?

    • The spring's stiffness increases steadily with extension
    • The spring's natural length increases with each force applied
    • In this region extension is directly proportional to force, so the stiffness is constant
    • Elastic strain energy is constant throughout the region

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