A 2.0 kg wood box slides down a vertical wood wall while you push on it at a 45 degree angle. What magnitude of force should you apply to cause the box to slide down at a constant speed? (Problem 51, Chapter 5, Knight) I can't figure out this problem and do not have the text to refer to (alibris.com sent me the wrong book). I'm not having problems with FBD's. I tried to set the acceleration to zero so it travels at a constant speed but with zero acceleration there is zero force. I'm confused.