NEEED HELPPP! what is a problem that i could investigate and test?? i have a two months to do it!!!?

im in grade 10 and the topic is science, i have to think of an idea and got 5 days to do it! cos i have to feel out some logg thing the teacher has to see this weeekk. an example of a problem that i cannot use is : buying 5 types of batteries and seeing which one is longer lasting. OR another example: planttss and the type of light. i need a problem and experiment that is similiar to thiss. it has to have a theory that can be tested. PLEASE HELP!! thankyou. ohh yeahh preferbaly not an idea that i have to test on MYSELF eg my skin and stuff like that . i want to test it with actual items