Question

Why is the body of cars, scooter s etc. is mounted on flat springs ?

Answer 1

The reason for this is that the flat springs (or leaf springs), absorb and compensate for irregularities on the surface of the road during the drive, support weight ensuring that there is no sagging, and also maintains the suspension system at a given required height. The result of this is a comfortable ride with an ease in handling the vehicle or scooter and also load bearing  ability. The leaf spring also attaches the axle to the rest of the vehicle.