Questions on Young’s Modulus

1 A 40 kg block of aluminium is hung from the end of a vertical 0.50 m long steel wire with a cross-sectional area
of 5.0 ¥ 10-5m2
(i) Find the stress and strain in the wire.
(ii) What is the increase in the length of the steel wire?
Young's modulus of aluminium : 7.0 ¥ 1010 Pa
Young's modulus of steel : 2.0 ¥ 1011 Pa
Tensile strength of steel : 3.0 ¥ 108 Pa
[6 marks]

2 (a) Explain the meaning of the terms tensile stress and tensile strain.
[4 marks]
(b)

The graph shows the relationship between tensile stress and tensile strain for a specimen of metal. Copy the graph
and label it with the following regions or points.
(i) Region of plastic flow
(ii) Fracture point
(iii) Elastic limit.

3 (a) Young’s moduli, elastic limits and tensile strengths of material all are quoted with the same units, pascals. 

Explain the differences between these three physical quantities.

4. 4 For a leg bone of length 0.50 m and diameter 30 mm estimate
(i) the maximum stretching force it can bear,
(ii) the maximum change in length before fracture occurs.
Tensile strength of bone : 1.7 ¥ 108 Pa
Young's modulus of bone : 9.4 ¥ 109 Pa

5 A mass of 10 kg is hung from the end of a thin strip of steel which is 0.20 m long, 10.0 mm wide and
1.00!mm thick.As a consequence the strip stretches by 0.01 mm.

Calculate the value for Young’s modulus of the steel

6 What are the stress, the strain and hence the approximate Young's modulus for a fibre of the protein elastin which
has a cross-sectional area l.0 ¥ 10-10 m2 and which is stretched to twice its original length by a force of5.0 ¥ 10-5 N?