I haven't started my investigation yet and haven't even decided on a topic. I thought determination of the acceleration due to gravity would be a quite a safe bet with the potential for lots of results but i think many people are doing this and was wondering if any one had some more exotic ideas that would also yield plenty of viable results.
Basically i need to start my investigation soon.
Is it allowed to do an investigation on more than one topic that aren't really related?

So any suggestions would be cool.