Itsminimum diameter is??

Question

A brass rod is to support  of a load of 400N. Its elastic limit is 4 × 10^8  N/ m2 its minimum  diameter  must be

Ans 1.13mm

Answer 1

Elastic limit is maximum stress or force per unit area within a solid material that can arise before the onset of permanent deformation.

Stress = F/A = 4 × 10⁸ N/ m²
F = 400N
A = πr² = πD²/4
So,
4 × 10⁸ N/ m² = 400N/(πD²/4)
D² = 400 x 4 / 3.14 x 4 × 10⁸ 
D² = 1.27 x 10^-6 
D = 1.13 x 10^-3​​​​​​​ m = 1.13 mm