Two physics students (mary at 52.0 kg and john at 90.7 kg) are 28.0 m apart. let each have a 0.01% imbalance in their amounts of positive and negative charge, one student being positive and the other negative. estimate the electrostatic force of attraction between them. (hint: replace the stu- dents by spheres of water and use the result of problem 31.) section 27-6 charge is conserved

Emmy kicks a soccer ball up at an angle of 45° over a level field. she watches the ball's trajectory and notices that it lands, two seconds after being kicked, about 20 m away to the north. assume that air resistance is negligible, and plot the horizontal and vertical components of the ball's velocity as a function of time. consider only the time that the ball is in the air, after being kicked but before landing. take "north" and "up" as the positive ‑ and ‑directions, respectively, and use ≈10 m/s2 for the downward acceleration due to gravity.