Below are some suggested materials for students looking to do preparation problems ahead of the Physics Olympiad.
Review your basic concepts from your high school physics textbook. Knowing your basics is very beneficial!
Make a Quizlet or some flash cards with some physics problems from main branches (mechanics, electromagnetism, thermodynamics, quantum, optics/wave, and astronomy). You can collect problems from your textbook or online resources.
As you go through the Quizlet problems, mark the ones that you find take you a longer time than others, think about and identify what is causing the extra time. Is it figuring out equations? Going down incorrect calculation paths? Pay attention to those problems, identify the hang-ups and smooth them out.
Make your own equation sheet from your physics lessons. Are there equations you don’t fully understand or have trouble with? Highlight these equations on your sheet, find resources that help you better understand them, and do as many practice problems that use these equations as possible.
Freshen up on your math skills, maybe do some longer algebra problems that you can check your work on. Make sure you can get through a longer problem without many sign errors and such. Physics involves algebra, and you wouldn’t want to get hung up on a physics problem you know because your algebra is rusty.