1. The problem statement, all variables and given/known data "You push a 325-N trunk up a 20.0 degree inclined plane at a constant velocity by exerting a 211-N force parallel to the plane's surface." What force must be exerted on said trunk so that it would slide down the plane with a constant velocity? In which direction should the force be exerted? 2. Relevant equations W=mg Fnet= ma I'm not really sure about this section. 3. The attempt at a solution I drew a free body diagram with the known forces that are acting on the object (the Normal--perpendicular to the inclined plane, and the weight straight down). I also drew in the supposed pushing force and the opposing frictional force. I aligned the diagram on a coordinate plane so that all forces lie on an axis EXCEPT the weight. I resolved the weight: Wx= 325cos70 Wy= 325sin70 And found the coeff. of friction: sum of all forces y-axis: Fnet= N + Wy Fnet= N-Wy Fnet= 0 sum of all forces x-axis: Fnet= Pushing force + Ff + Wx Fnet= Fp + Wx - Ff ma= Fp + Wx -Ff (velocity is constant--> there is no acceleration): 0= Fp + Wx - Ff 0= 211 - (325cos70) - Ff Ff= approximately 100 N, the coeff of friction is thus approximately .3278 I am totally stuck now, though on how to find the force needed to cause the trunk to slide down the plane with constant velocity. . . . And I might have done something wrong above. :( Please help!