<p>I'm desperately studying to pass the next USAPhO semifinal exam. But there are very little information and resource about the exam, so I can do nothing but solve the past exams and problems in the book of Irodov and S.S. Krotov's Aptitude Test Problems in Physics. After using these books for several months, I cannot still perfectly solve problems of past exam, and the percentage of correct answers of mechanics problems was especially low.To improve the low percentage of correct answers, I want more past exams. But the number of exams are limited. Do you know some other effective resource for this exam? </p>
<p>Actually, I don't know about this exam at all except about the range of possible questions. Do you know what the cutoff is? I heard the cutoff of the semifinal largely fluctuates every year. Can I pass it by getting about 70% or even 60%? Partial credit can be given? International students are allowed to take the semifinal exam? (I know that they cannot join in the US Physics Team.)</p>