How Do You Find a Specific Horizontal Distance in a Projectile Problem?

[Jason03]

When you have a basic projectile problem, What is the easiest way to find a specific horizontal distance in the problem.( other than the full horizontal distance that the projectile travels)

Say you know the height (y) but want to find the distance (x).

 

[alphysicist]

In the basic projectile problems, the horizontal and vertical motions are independent of each other; but if along its path the particle is at the point (x,y), then that means that the time it is at x is the same time it is at y.

So if you know the height, find out at what time it is at that height; then find out how far horizontally it has gone in that time.