I am a high school senior. One of my friends did a research project in a certain field of Computer Science 2 years ago and it won a lot of awards. He is now at university. I read his paper and relevant work in the area and the research area looks really interesting. I want to do research that's closely related to this idea and I have a few ideas on how to extend the research. Is it ethical to do this project? My main concern is that he/other mutual friends will think that I just used the same idea so that I could win as well.
Yes, you can do this. You are not taking his ideas, you are using your own (note you wrote "I have a few ideas").
Basically, once a paper is published, all the ideas within becomes public knowledge and you are free to build on them. You should still cite the original paper if you are building on their ideas, but your extensions are yours and yours alone.
By the way, many authors will be quite flattered if you work on their ideas - it implies that you find their ideas interesting.
Good part of research done is based on or similar to many other studies done before. Actually, most papers cite and compare the results with many other similar researches. If you do another research and cite them properly they should feel honored unless your are really just copy-pasting / plagiarising. In fact, research papers' quality and influence is generally measured by quantity of citations it got in other papers.
This is of course not a problem! In fact, it's exactly how scientific research works. I would say there are two things you definitely should do to avoid any ethical concerns:
- Clearly cite your friend's previous work.
- Provide a fair review of the work your friend did as a part of your project and presentation. Emphasize what they accomplished and how your work fits in or extends the existing research.
As long as you do those two things, there are no ethical qualms with doing this project.