physics
posted by kb .
An airplane is flying horizontally with a constant velocity of 160 m/s at an altitude of 5400 m when it drops a package.
How far ahead of the target along the x direction should the plane be when it releases the package?

Calculate how long it takes to hit the ground. Call that time T.
Use H = (1/2) g T^2
Rearrange it to solve for T. H is 5400 m and you should know what g is.
Multiply T by the horizontal flight velocity, 160 m/s.
That will tell you how far the box moves forward along the flight path while it is falling.