Question

Two wires are made of the same material and have the same volume. However wire 1 has cross-sectional area A and wire 2 has cross-sectional area 3A. If the length of wire 1 increases by Δx on applying force F, how much force is needed to stretch wire 2 by the same amount?(a) 4 F(b) 6 F(c) 9 F(d) F

Answer 1

Answer:

C) 9F

Explanation:

Since the two wires have the same volume.  Thus,

Length of wire 1 =l

Length of wire 2 =l/3

Area of wire 1 =A

Area of wire 2 =3A

Wire 1 = F/A/ Δx/l

Wire 2 = F1/A/ Δx/l/3

Therefore,

F/A×l/Δx = F1/3A×l/3Δx

F1 = 9F

Thus, the force needed to stretch wire 2 by same amount is 9