Which of the following statements is correct?
- AThe stress is the pressure per unit area
- BThe strain is expressed in mm
- CHook’s law holds good up to the breaking point.
- DStress is directly proportional to strain within elastic limit.Correct
Solution
Concept
Fundamental relationship between stress and strain
Formula
NONE
Step-by-step solution
1. Hooke's law defines the linear relationship between stress and strain in elastic materials. 2. It states that stress is directly proportional to strain up to the proportional limit/elastic limit of the material. 3. Strain is dimensionless, stress is internal resistance per unit area, and Hooke's law fails beyond the elastic limit. Answer: D
Explanation
Hooke's law states that for an elastic material, stress is directly proportional to strain up to the elastic limit. Options A and B are incorrect because stress is internal resisting force per unit area and strain is a dimensionless ratio. Option C is incorrect because Hooke's law breaks down past the elastic limit well before the breaking point.
Why the other options are wrong
A) Stress is internal resisting force per unit area, whereas pressure is an applied external force. B) Strain is a dimensionless quantity without units. C) Hooke's law holds true only up to the proportional limit, not the breaking point.
Shortcut
Hooke's Law states that stress is directly proportional to strain within the elastic limit.
Common mistake
Incorrectly believing Hooke's law applies up to the ultimate breaking point instead of the elastic limit.
Correct answer: D) Stress is directly proportional to strain within elastic limit.