Practice Test 9

Two plastic rods are rubbed with cloth and then brought near each other. Sometimes they repel and sometimes they attract depending on how they were charged. A student wants to investigate how distance affects electric force strength using only the rods and a ruler. Which question is most investigable?

A student writes this investigation question after seeing a rubbed balloon attract paper: “How does rubbing time and distance and wall material affect electric force?” Which change would make the question more testable and focused?