Question 18
A rectangular block of steel supporting a very large component of a bridge has a height of 15 cm and a cross-section of 20 cm × 12 cm. It is designed to compress 1 mm when under maximum, evenly distributed, load.
The Young modulus of steel is 2.0 × 1011 N m-2.
What is the maximum load it can support?
A 32 MN B 56 GN C 720 GN D 32 TN
Reference: Past Exam Paper – November 2017 Paper 12 Q21
Solution:
Answer: A.
Length L = 15 cm = 0.15 m
Cross-sectional area A = (0.20 × 0.12) m2
Compression, e = 1 mm = 0.001 m
Young modulus E = 2.0×1011 N m-2
Maximum load F = ???
Young modulus E = stress / strain = FL / Ae
E = FL / Ae
F = EAe / L
F = (2.0×1011 × 0.20×0.12 × 0.001) / 0.15
F = 32 000 000 N = 32×106 N = 32 MN
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