Hooke's Law and Elastic Limit

Steps:

• Identify the graph as extension e versus load L, showing linear increase initially.
• Recall Hooke's law: stress proportional to strain within elastic limit, so e proportional to L.
• Note the straight line indicates proportionality until a point, beyond which it curves (plastic deformation).
• Determine the property tested by the linear region.

Why C is correct:

• C states the rod obeys Hooke's law up to the elastic limit, matching the linear graph per F = kx.

Why the others are wrong:

• A: Incorrect, as the graph shows initial linearity, not constant extension.
• B: Wrong, since extension increases with load, not decreases.
• D: False, the curve indicates exceeding elastic limit, not purely elastic throughout.

Final answer: C