Has anyone done 2008 F=ma contest?

[maruhan2]

I've been practicing for 2009 F=ma contest (Physics Olympiad preliminary test) by doing 2008 test but the last 10 problems are TOUGH
I couldn't solve any of them correctly
Can anyone help me with them?

 

[jtbell]

Try posting individual problems and your attempt at solving them in the appropriate forum in the "Homework and Coursework Help" section. One problem per thread, please, and it's probably a good idea to focus on one problem at a time instead of trying to do several at once.