1. The problem statement, all variables and given/known data A 500 g rock falls out of a 75 m tree. It takes it 5s to parachute to the ground. How much friction is upon it? 2. Relevant equations Fnet=ma Fg=mgh possibly [tex]\Delta[/tex]d=v1[tex]\Delta[/tex]t+.5a([tex]\Delta[/tex]t)2 and other kinematics formulas 3. The attempt at a solution I tried to find the net force, using 9.8 m/s2 as a, then gravitational force. I subtracted the gravitational force from the net force, which did not work at all. Next I tried to find a using a kinematics formula, and use that number to find the net force and subtract the new gravitational force from it, but still did not get a good answer.