Question

A metal bar is elongated by 2mm when put under a certain amount of tension. How much will it be elongated if the tension is doubled?

Answer 1

Answer: 4mm

Explanation: From Hooke's law.

Tensile force is directly proportional to the elongation

That's

F= k e ， where k is constant

F/e = k

F1/e1 =F2/e2

Where e1 = 2mm

F2 =2F1 (doubled)

F1/2 = 2F1/e2

1/2 =2/e2

e2 = 4mm

Therefore when tension is doubled, the metal bar will be elongated by 4mm