1. The problem statement, all variables and given/known data A projectile of mass 1.350 kg is shot straight up with an initial speed of 13.0 m/s. (a) How high would it go if there were no air friction? I found this to be 8.622 m. (b) If the projectile rises to a maximum height of only 7.4 m, determine the magnitude of the average force due to air resistance. 2. Relevant equations u + k = u + k 3. The attempt at a solution I found the difference in potential energy at m = 7.4 and m = 8.622, which equals the work done. I then solved for F in the formula W = F D cos theta. What did I do wrong?