1. The problem statement, all variables and given/known data When the elevator is at rest, the scale reads W. Suppose the elevator now accelerates down-ward at a constant rate of 0.4 g. What is the ratio of the new scale reading to the value W of the scale reading when the elevator is at rest? 2. Relevant equations Force equations: F = ma Fnet = 0 3. The attempt at a solution What I did is to draw a force diagram that resulted: At rest: Fn - mg = 0 mg = Fn Accelerating: Fn - mg = -ma, where a = .4g mg = Fn + .4mg I set Fn = mg = 1, so ratio becomes to 1.4 -> (1 + .4)/(1) The real answer is .6, but I'm not really sure how to get that. I know if I do: Fn - mg = ma mg = Fn - .4mg, the ratio then becomes to .6 Why is it "ma" instead of "-ma" when the elevator is accelerating downwards?