Help..Interesting physics research project?

Hi.

I am sorry if my english is not perfect...it is not my 1st language

I am a high school student

For physics we need to do a research on any subject we would like.

I love physics very much and that is why I want a very interesting project. We also have an expo. We will promote our project to a lot of people.

But my final grade is for something I have to research. I will also need to do a practical reasearch on my project and decide the correlation between things... for example efficieny of an engine or number of nodes in a standing wave as a function of the tension in the string.

So can you please help me find a subject. I would love a challenge... but nothing impossible to build. Thanks a lot!!