The manager of a department store is pushing horizontally with a force of magnitude 200 N on a box of shirts. The box is sliding across the horizontal floor with a forward acceleration. Nothing else touches the box. What must be true about the magnitude of the force of kinetic friction acting on the box (choose one)? (a) It is greater than 200 N. (b) It is less than 200 N. (c) It is equal to 200 N. (d) None of those statements is necessarily true.

Week 4 Tuesday, September 13, 2016 10:45 AM E field of nonconducting infinite plane sheet of charge: Pos charge per unit area Symm analysis: Made up of infinite number of point charges Field must be perpendicular to sheet Field is directed towards or away from sheet For cylindrical gaussian surface: Flux thru ends is EA , no field thru curved part of surface Field is away from sheet Find field above/belowsheet with uniform negative charge per unit area (cylindrical) Same as above: sum top bottom and side. But E will be negative in bottom equation bc field is pointing towards sheet Parallel Plate Capacitor- plates of neg and pos charge w same c