1. The problem statement, all variables and given/known data A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.78 of the person’s regular weight. a. Calculate the acceleration of the elevator. b. Find the direction of acceleration. 2. Relevant equations Sum of forces. 3. The attempt at a solution I know the equation is F_normal-mg=ma but don't understand how it was derived.