Question

How does the long shape of submarines and torpedoes reduce the dragthey feel when moving under water?

Answer 1

In the front side of the submarines and torpedoes, the small area of contact is maintained to reduce the pressure or the drag force on the submarines due to the water.

The drag force in terms of the area of cross-section of the submarine is,

$F_d\propto A$

where F_d is the drag force acting on the submarine and A is the area of cross-section of a submarine in contact with the water,

There is also piped formation that takes place through which the water runs lengthwise while the submarine is moving in the forward direction, thus, reduces the force on the submarine due to the water.