All flashcards topics

The Young modulusAQA A-Level Physics: Flashcards

What these 13 flashcards ask

  • Define tensile stress.
  • Define tensile strain.
  • State the equation for the Young modulus.
  • What is the unit of the Young modulus?
  • Why is the Young modulus a property of the material, not of the sample?
  • What does a steeper stress–strain line indicate?
  • How is E found from a graph of stress against strain?
  • How is E found from a graph of force against extension?
  • What happens to the extension of a wire if its diameter is doubled under the same load?
  • Which instrument should be used to measure the diameter of the wire in Required practical 4?
  • Why is the diameter the largest source of uncertainty in the Young modulus practical?
  • Why is a long, thin wire used in the Young modulus experiment?
  • Why must the loads stay within the limit of proportionality?

Exam questions on The Young modulus

  1. A steel wire of length 2.50 m and diameter 0.80 mm hangs from a fixed support and carries a load that produces a tension of 40 N. The Young modulus of the steel is 2.0 × 10¹¹ Pa and the wire obeys Hooke's law.
    Calculate the extension of the wire.2 marks
  2. Two rods, X and Y, have identical lengths of 1.50 m and identical cross-sectional areas of 2.0 × 10⁻⁵ m². The Young modulus of X is 1.0 × 10¹¹ Pa and the Young modulus of Y is 2.0 × 10¹¹ Pa. Both rods are used within the limit of proportionality.
    Calculate the force needed to produce an extension of 0.80 mm in rod X.2 marks
  3. A student determines the Young modulus of a copper wire. The wire is fixed at one end and passes over a pulley at the other end, where masses are added in steps. The unstretched length from the fixed end to a marker is 1.85 m. The student measures the diameter of the wire with a micrometer and obtains a mean value of 0.30 mm. A graph of force against extension is a straight line through the origin with a gradient of 4.5 × 10³ N m⁻¹.
    Explain how the student should measure the diameter of the wire, and why this measurement is likely to be the largest source of uncertainty in the Young modulus.3 marks
See the full worksheet

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).