1. The problem statement, all variables and given/known data "The work done by static friction can be: a) positive b) negative c) zero d) nonnegative e) any of the above 2. Relevant equations W=F*d F(friction)= μ *FN 3. The attempt at a solution I thought the answer must logically be "c) zero" because static friction has no distance for as soon as movement begins static friction ends and as such there can be no work without distance. This is for a test correction and so my teacher has told me the correct answer is "e) any of the above" but I must explain why. I think it must have something to do with the wording of the question or a special circumstance in which static friction is considered to do work.