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CAIE A-Level Physics AS 6.2 Elastic and Plastic Behaviour Questions

Practise interpreting loading curves, elastic limits and permanent deformation, finding work from graph area and calculating stored elastic energy.

Syllabus
2028–2030
Course
Physics 9702
Level
AS

Exam points

  • distinguish elastic and plastic deformation and identify the elastic limit from a graph or from what happens when the load is removed
  • interpret the area under a force–extension graph as work done and calculate areas for simple or irregular graph regions
  • determine elastic potential energy from graph area or from EP = 1/2Fx = 1/2kx² within the limit of proportionality

Covered syllabus points

6.2.1—The terms elastic deformation, plastic deformation and elastic limit6.2.2—The area under the force–extension graph represents the work done6.2.3—The elastic potential energy of a material deformed within its limit of6.2.4—EP = 1/2 Fx = 1/2 kx2 for a material deformed within its limit of

Question 1

[Maximum number: 1]

A sample of metal is subjected to a force which increases to a maximum value and then decreases back to zero. A force-extension graph for the sample is shown.

Figure for Question 1 — CAIE A-Level Physics AS

When the sample contracts, it follows the same force-extension curve as when it was being stretched.

What is the behaviour of the metal between X and Y ?

A

both elastic and plastic

B

not elastic and not plastic

C

elastic but not plastic

D

plastic but not elastic

Question 2

[Maximum number: 1]

A sample of material is stretched by a tensile force to a point beyond its elastic limit. The tensile force is then reduced to zero. The force-extension graph is shown.

Figure for Question 2 — CAIE A-Level Physics AS

Which area represents the net work done on the sample?

A

X

B

X+Y

C

Y+Z

D

Z

Question 3

[Maximum number: 1]

A length of metal wire is attached to a fixed point and hangs vertically. Masses are then suspended from the wire. Assume that the cross-sectional area of the wire remains constant.

Figure for Question 3 — CAIE A-Level Physics AS

A stress-strain graph for the wire is plotted, as shown.

Figure for Question 3 — CAIE A-Level Physics AS

What is represented by the shaded area under the graph?

A

strain energy in the wire

B

 strain energy in the wire  cross-sectional area of the wire \frac{\text { strain energy in the wire }}{\text { cross-sectional area of the wire }}

C

 strain energy in the wire  original length of the wire \frac{\text { strain energy in the wire }}{\text { original length of the wire }}

D

 strain energy in the wire  original volume of the wire \frac{\text { strain energy in the wire }}{\text { original volume of the wire }}

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