posted by jameson .
A gun shoots bullets that leave the muzzle with a speed of 341 m/s. If a bullet is to hit a target 171 m away at the level of the muzzle, the gun must be aimed at a point above the target. How far above the target is this point?
The time it takes to reach the target is 171/341 = 0.502 s
Calculate how far the bullet falls in that time. That is how high you should aim, above the target.