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CAIE A-Level Physics 6.1.5 Stress, Strain and Young Modulus

Practise calculating tensile stress, strain and Young modulus, interpreting material data and using dimensions, graphs and measurements to find unknown values.

Syllabus
2028–2030
Course
Physics 9702
Level
AS

Exam points

  • calculate stress as force divided by cross-sectional area and strain as extension divided by original length
  • define and use Young modulus as stress divided by strain, with correct units
  • interpret stress–strain or force–extension data to compare materials and identify proportional, elastic or failure behaviour
  • use dimensions, graphs and measured quantities to determine an unknown Young modulus, stress, strain or extension

6.1.5—The terms stress, strain and the Young modulus question 1

[Maximum number: 2]

Fig. 4.1 shows the variation with extension x of the tensile force F for two wires, G and H, made from the same material.

Fig. 4.1

Fig. 4.1

The elastic limit has not been exceeded for G or H.

Wires G and H are joined together end-to-end to form a composite wire of negligible weight. The composite wire hangs vertically from a fixed support.

A block of weight of 2.0 N is attached to the end of the wire, as shown in Fig. 4.2.

Fig. 4.2

Fig. 4.2

The original length of wire G is L and the original length of wire H is 1.5 L.

Calculate the ratio

 cross-sectional area of wire G cross-sectional area of wire H\frac{\text { cross-sectional area of wire } \mathrm{G}}{\text { cross-sectional area of wire } \mathrm{H}}
ratio =
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