Two wires are made of the same material and have the same volume. The first wire has cross sectional area A and the second wire has cross sectional area 3A. If the length of the first wire is increased by Deltal on applying a force F, how much force needed to stretch the second wire by the same amount ?

Two wires are made of the same material and have the same volume. The

1.	Two wires are made of the same material and have the same volume. The first wire has cross sectional area A and the second wire has cross sectional area 3A. If the length of the first wire is increased by Deltal on applying a force F, how much force needed to stretch the second wire by the same amount ?
Answer» F 9F 4F 6F Solution :Young.s MODULUS `y=F/(A DELTAL)` but `V=Al rArr l=V/A` `THEREFORE y=(FV)/(A^2Deltal)` `therefore F=(yA^2 Al)/V`, y , `Deltal` and V CONSTANT `therefore F prop A^2` `therefore F_2/F_1=(A_2/A_1)^2 = ((3A)/A)^2=9` `therefore F_2=9F "" [ because F_1=F]`