1. The problem statement, all variables and given/known data A 90 kg parachutist in free fall has an acceleration of 6.8 m/s^2. 2. Relevant equations What is the frictional force provided by air resistance when she is accelerating at this rate? 3. The attempt at a solution I tried this, assuming down is positive. I used the equation Ff=mg-ma, and I got the answer 270 N, but I thought frictional force was supposed to be in the opposite direction of the gravitational force. So shouldn't it be negative?