Once her chute opens, a sky-diver of mass m is acted upon by a downward force Fg due to gravity, and an upward force Fr due to air resistance. If Fg = mg, where g is gravitational acceleration, and Fr is proportional to velocity v, use Newton’s Second Law of Motion to write acceleration a as a function of velocity v. Hey guys, I need a help on how to approach this problem. Initially, I assumed Fr = Ff = umg. But the problem states that Fr is proportional to velocity. Help?