Two wires are suspended from the ceiling (see figure). The wire on the left is made of copper, its length is 2 m, its cross-sectional area is 
and a weight of 10 kg is hung on it. The wire on the right is made of aluminium, its length is 3 m, and its cross-sectional area is 
. What is the mass of the weight that we have to hang on the second wire so that its extension is the same as the first wire? The Young modulus of copper is 
and that of aluminium is 
.
is required on the second wire to give an equal extension with the first wire.
