OR: When a rifle is fired at a distant target, the barrel is not lined up exactly at the target. Why not? Does the angle of correction depend on the distance of the target?
If a rifle is fired at a distant target keeping the barrel lined up exactly at the target, the bullet will not hit the target. It will hit below the target. It is because as the bullet moves forward, it also moves a vertical downward displacement due to gravity. At a certain time $t$, it falls a certain height given by $\frac{1}{2}gt^2.$
[Read: Motion Under Gravity]
So, the man should point his rifle above the target. The angle of correction also depends upon the distance of the target.
[Read: Projectile Motion]