Question

railway tracks are mounted on sleepers reason

Answer 1

this is because wooden sleepers increase the area on which pressure of train is to be exerted.Thus pressure is not concentrated on a single point densely.therefore if there more area there would be less pressure and train will run smoothly.

Answer 2

Wooden sleepers are set below railway tracks so that the pressure exerted by  the rails on the ground becomes less and the railway lines do not sink into he ground so that accidents can be avoided.