Question

A force Fis needed to break a copper wire having radius
R. The force needed to break a copper wire of radius 2R
will be
(1) F/2
(2)2F
(3) 4F
(4) F/4​

Answer 1

Answer:

Stress = Force / Area = F/A = F/ pi R^2 --> 1

For radius R, force needed = F

For radius 2R, force needed will be

Stress = F' / pi ( 2R) ^2

Stress = F'/ pi 4R^2 --> 2

F / pi R^2 = F' / pi 4R^2

F' = 4 F

❇ 3rd option is the correct answer.