Strength Of Materials MCQ Questions & Answers | Mechanical Engineering

The Factor of Safety (FoS) is a measure used in engineering to ensure that structures or components will perform safely under expected loads. It is defined as the ratio of the ultimate stress (the maximum stress a material can withstand before failure) to the working stress (the stress that the material is expected to endure during normal use).

Factor of Safety Formula:
The formula for Factor of Safety is:

FoS = Ultimate Stress / Working Stress

This ensures that the component or structure has enough strength to handle unexpected loads or conditions safely.

Option B: Working stress to ultimate stress
This option is incorrect as it represents the reciprocal of the Factor of Safety.

Option C: Breaking stress to ultimate stress
Breaking stress is essentially synonymous with ultimate stress, so this option does not correctly describe the Factor of Safety.

Option D: Ultimate stress to breaking stress
Since breaking stress and ultimate stress are the same, this option also does not describe the Factor of Safety correctly.

Therefore, the correct answer is Option A: Ultimate stress to working stress.

Stress is nothing but the resisting force since due to temperature rise body will expand and if this expansion due to temperature change is restricted then only resisting stress (thermal stress) will come into play since expansion is not restricted that's why no stress is occurring.