Question 5
Part 1: Candidates were required to answer any five questions from this part.
Explain the following terms:
- tensile stress;
- young’s modulus.
Observation
A good number of candidates scored full marks in this question. However, some lost mark by not making reference to ‘a wire/rod’ in their definition. Hence they failed to recognise the implication of the word ‘tensile’ which makes it different from ‘shear’ and ‘bulk’ stress. Few others failed the part (a) for using the word ‘area’ instead of ‘cross – sectional area’ and part (b) for omitting ‘tensile’ in their definition.
The expected answers are:
- Tensile stress is the ratio of force to cross-sectional area of a wire/rod
It is expressed in newton per metre squared (Nm-2)
- Young’s modulus is the ratio of tensile stress to tensile strain
- It is expressed in newton per metre squared (Nm-2)