Diagram of a table and a marble

For my high school physics project, we are doing a project to see how consistently we can roll a ball at 1 m/s. We are testing how fast we roll the ball,< by calculating it's trajectory off of a table as it falls due to the acceleration of gravity.

My physics teacher expects us to hand in a diagram of the problem. He always expects that everything is computer generated (or we will not get an A).

So, my question is: What would be the best way for me to create such a diagram. (using the tools available to me on the gnu/linux operating system).

I have no prior graphics experience, and this is due by Thursday. (He assigned the project an hour ago, so, no I did not procrastinate).
So obviously I can not use something which is going to take me longer than till then to figure out how to make the diagram.

Right now I'm trying to find a stock photo of a marble on a table so I can create an overlay of arrows to show the trajectory, etc.

Any suggestions, comments, etc. would be greatly appreciated.

Thank you for your time and effort,

Joseph Pond

I think you're asking what programs to look for. If that's the case, grab the GIMP for image creating/editing. You can also take a look at Inkscape for vector graphics.

EDIT: links
http://www.gimp.org/
http://www.inkscape.org/