Two wires of equal cross section but one made of steel and the other of copper, are joined end to end. When the combination is kept under tension, the elongations in the two wires are found to be equal. Find the ratio of the lengths of the two wires. Young modulus of steel `=2.0xx10^11Nm^-2` and that of copper `=1.1xx10^1Nm^-2`

Answer

20//11

Explanation

`Y_s = (F)/(A) xx (l_s)/(Delta l_s) , Y_c = (F)/(A) xx (l_c)/(Delta l_c),`
`So, (Y_s)/(Y_c) = (l_s)/(l_c) xx (Delta l_c)/(Delta l_s) = (l_s)/(l_c) ( :. Delta l_c = Delta l_s)`
`:. (l_s)/(l_c) = (Y_s)/(Y_c) = (2.0xx 10^(11))/(1.1xx 10^(11)) = (20)/(11)`