Before you begin, you need to first figure out what your problem gives you and what you need to look for.
Given:
vix=10m/s
dy= 20m
What you are looking for is horizontal distance or dx.
The formula for vertical distance is:
Where:
dx= horizontal distance
vix= initial horizontal velocity
t=time
But when you look at your problem, you do not have time. Now for time, you need to use the formula:
g in this equation is a constant. It is the acceleration due to gravity which has the value of 9.8m/s^2.
Now we first need to get time:
Now that you have time, all you need to do is insert that into our equation for horizontal distance.
The horizontal distance of the rock will be
20.20m.