The Young modulusAQA A-Level Physics: Mind map

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