The engines may indeed push the plane, but if the plane is on a conveyor belt moving in the opposite direction at the same speed that the engines are pushing the plane, it's still not gonna go anywhere. Unless it's a harrier jump jet - British Engineering can overcome this scenario

Me and my friend at work have been arguing about one of these kinda things for a few weeks now.

He says that if you fire a bullet from a gun perfectly level with the ground, then drop a bullet from the same height at the same time, both will hit the ground at the same time, as the Gravitational pull on both bullets is the same.

I call Bullshit as the aerodynamic flow over the bullet and the velocity of the bullet has to play into it somewhere.