A wire elongates by l mm when a load W is hanged from it. If the wire goes over a pulley and two weighs W each is hung at the two ends, the elongation of the wire will be (in mm) (a) l/2 (b) l (c) 2 (d) zero

Y = (Force x L)/(A x l) = WL/Al

l = WL/AY

Due to the arrangement of the pulley, the length of wire is L/2 on each side and so the elongation will be l/2. For both sides elongation = l

Hence, the correct answer is option (b)