Welcome to PF;
This is part of your education right?
Therefore, you should come up with the project: we can help you make a decision and design the project but it has to be your own work.
Your initial problem comes from how the field is wide open - when you can do anything you want (pretty much) it is hard to think of something you want to do.
Start with what sorts of things interest you.
One of the things that computers are good at is crunching numbers where you'd normally have to make an approximation. For instance, how do pendulums behave when the angle is not small? Where the bob is not point-like? How do light rays behave when they are far from the optic axis and the lens is not thin? How does a projectile behave when air resistance is not negligible? ... you may prefer something different but do you see what I mean?
Take a look through your course for the bits where you had to use an approximation, and see if you can get your computer to model the situation where the approximation does not hold.
From there you can work out what sort of practical experiment to use to test the resulting model.
You will presumably have a limited budget - also look at the resources already available in the school.
Helps to pick something you are interested in doing too.
When I was in high school I launched rockets - which may be illegal where you are - so have fun.