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 Ax on
applying force F, how much force is needed to stretch wire 2 by the same amount?

Please righy the answer on copy click a photo of the answer then add answer

Answer 1

Answer:

As shown in the figure, the wires will have the same Young's modulus (same material) an the length of the wire of area of cross-section 3A will be l/3 (same volume as wire 1).

For wire 1,Y=△x/lF/A.....(i)

For wire 2,Y=△x/(l/3)F′/3A....(ii)

From (i) and (ii), AF×△xl=3AF′×3△xl⇒F′=9F.