The work done in stretching a wire by 0.1 mm is 4 J. Find the work done (in J) in stretching another wire of same material, but with double the radius and half the length by 0.1 mm in joules.

Work done W=12Fx (F is force, x is elongation)Here elongation is same and W∝FBut elongation is given by =FlAYAs x, Y are constants F∝AlIf F1 and F2 are the forces in the first and second cases           F1F2=A1A2×l2l1=r12r12×l1/2l1=14×12=18Then  W1W2=F1F2=18W2=8W1=8×4=32 J