Your on a train travelling @ 100mph & shoot a bullet out the window in the opposite direction would it stop?

This is a drunken pub arguement which has been on going for months. The train is moving forward at 100mph and the bullet is fired in the oppositre direction to which the train is travelling, and for arguments sake the bullet is fired from the gun at 100mph. Would the bullet stop or fall to the ground?

yup

It wont suddenly stop and fall to they ground. As it gets less faster due to like air resistance etc. gravity will affect it more and it therefore will slowly curve downwards, then hit the ground

No.... it wouldnt.
Even if you going at the same speed, the momentum just wouldnt disappear would it? It'd keep going...
Newtons 2nd Law.... For every action there is a equal and opposite reaction.

the bullet would still be traveling at 100 mph relative to the muzzle of this mythical pistol. if you fired it in the direction that the train was traveling it would appear to be traveling forward at 100 mph until the inertia of the bullet was expended/cancelled. when the inertia of the bullet was expended it would fall to the ground.
if you fire the bullet toward the back of the train it would appear to move toward the caboose at 200 mph.

No it would just act the same as a bullet fired from a stationary position at that point, like the question though, had me thinking

The movement of the bullet is relative to what your reference point is. If the reference point is you, the bullet will move as if you're not moving (you'll see it moving at 100mph). That is because you are in equilibrium (that means you're not accelerating.. if you're not accelerating, you will not be able to tell if you're moving unless you look outside.. in other words, everything that is happening in a moving but not accelerating body is the same if the body is not moving). If your reference point is the ground, it would just fall straight downward (of course if the bullet did not hit the train's wall or something).

"would the bullet stop or fall to the ground?" --am i asked to choose between the two? okay... try holding a rock, drop it (do not throw, just drop). that is what will happen if you're looking at the bullet while standing on the ground. yes, it will stop moving horizontally... but it will accelerate downward due to gravity.