Question

the shape of an aeroplane is not keep the same as the shape of bus why​

Answer 1

Boats and aeroplanes are streamlined so as to reduce fluid friction.

Aeroplanes, boats, fishes and birds which move through fluids have bodies of special shape, called streamlined shape, so as to reduce the friction due to fluid and avoid energy loss.

For example,if the boat isn't streamlined, then it also has to push the water out of its way, increasing the drag force.