Question

A and B are two wires. The radius of A is twice that of B. They are stretched by the some load. Then the stress on B is

• A. Equal to that on A
• B. Four times that on A
• C. Two times that on A
• D. Half that on

Answer 1

Answer: (B)

Four times that on A

Answer 2

Stress $= \frac { \text { force } } { \text { Area } }$∴

$\frac { S _ { B } } { S _ { A } } = \left( \frac { r _ { A } } { r _ { B } } \right) ^ { 2 } = ( 2 ) ^ { 2 } \Rightarrow S _ { B } = 4 S _ { A }$