A trolley wire weighs 1 kg per metre length. The ends of the wire are attached to two poles 20 m apart. If the horizontal tension is 1000 kg, the central dip of the cable is

ANS:D - 5 cm

For a cable supported at both ends it buckles to resemble shape of catenary but if the dip is small then it can be approximated to a parabola which boils down to equation [(w*l*l)/(8*d)]=T where d is central dip , T is tension generated in cable and w is the UDL of cable and l is length between supports, using this formula we get answer as 5 cm.