Click Play to start the simulation. Enter the time when you think those two particle have the same HORIZONTAL speed. (Enter into the text field and the answer will be shown).
You can change the initial velocity for both particle with your mouse (drag the RED arrow).
The horizontal velocity for the top one should be larger than the lower one.
The top one will move with constant velocity, while the second will need to move up the hill (with constant deceleration a=-g*sin?)
You can also drag the yellow box to change the height of the slope.
Two traces shows X(t) for both particles.  Try to find out the answer from those two curves.

Type in your answer then click to find out the result
VIEW or DOWNLOAD ejs xml source
then click to translate strings for selected locale.

Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop.

*** Remember: [color=red]You need to hit [b]ENTER[/b] after you enter the value[/color]. (the box turn yellow if you did not hit ENTER)

I hope you got the correct answer!  :)