Hello, I have a problem that I am stuck with. The problem consists of a 2.60kg box sliding across the horizontal floor of an elevator. The coefficient of kinetic friction between the floor and the box is 0.490. I have to determine the kinetic frictional forces of different cases. (a) when the elevator is stationary ------Which I have already done. That part was easy. but I'm stuck on the following two. (b) when the elevator is accelerating upward with an acceleration of 1.30 m/s^2 (c) when the elevator is accelerating downward with an acceleration of 1.30 m/s^2. I assumed that I could use the equation, kinetic frictional force = kinetic friction times mass and acceleration. That however was not correct. Any help or direction provided would be greatly appreciated.