Alright guys if the locomotives have their front surface completely straight then the force acting over it is maximum in some cases might not cause locomotion move but if it has an angle of 45' the force reduces to half but if it reduces to 30' or something less still it remains same . So does it mean that the force acts maxima 45' only.

i would be more concerned about the drag induced by the sides and rear of the train.

Alright guys if the locomotives have their front surface completely straight then the force acting over it is maximum in some cases might not cause locomotion move but if it has an angle of 45' the force reduces to half but if it reduces to 30' or something less still it remains same . So does it mean that the force acts maxima 45' only.

 

I do not think it remains the same. But the difference between 45 and 30 degrees may be so small that locomotive manufacturers don't want to spend the money to make the nose longer (the front at 30 degrees will be longer than at 45 degrees).

 

Here's a graph (it's the 2nd on the page) showing the drag coefficient as a function of the angle of attack.

Then we can build our jets with the airfoil angle being the least for the minimum force

Yes. There are two basic forms if drag, parasitic and induced. One is parasitic is related directly to speed while induced is inversely related. At some point you get the perfect balance between two different designs. Same with planes, trains and automobiles. At some point, it isn't cost effective to keep changing the angle or shape.