Two wires A and B are made of same material having ratio of lengths LALB = 13 and their diameters ratio dAdB = 2. If both the wires are stretched using same force, what would be the ratio of their respective elongations?
- 3 : 4
- 1 : 12
- 1 : 3
- 1 : 6
Answer
(2) 1 : 12
Solution
Young's modulus: Y = FLA L ⇒ L = FLAY = 4FL d2 Y
Same material (same Y) and same force F:
L Ld2
⇒ LA LB = LALB ( dBdA )2
= 13 ( 12 )2 = 112
∴ LA : LB = 1 : 12
Answer: (2)