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A man grows into a giant such that his linear dimensions increase by a factor of 9. Assuming that his density remains the same, the stress in the leg will change by a factor of

Asked in JEE Main 2017 · Stress and strain

Answer: (1) 9

Step-by-step solution

The stress in the leg is the weight carried divided by the cross-sectional area of the bone.

At fixed density the mass follows the volume, so the weight scales as L³ and grows by 9³=729.

A cross-section is an area, so it scales as L² and grows by 9²=81.

Stress ∝(L³)/(L²)=L, so it changes by the factor 9.

This is why giant creatures are not just scaled-up people: the stress in the bones rises in proportion to size.

Why the other options are wrong

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