The
figure at the right shows a box on an inclined plane (or "ramp")
with a horizontal applied force, FA, pushing it up the
incline. A coordinate system is also shown, with +x downhill and parallel
to the incline. +y is perpendicular to the plane and pointing above it.
The force of gravity, Fg, is shown as are two components of the force by the surface, called FRAMP. The two components are FN and FFr, the normal force and the friction force, respectively. Because they are components, the two ramp forces are not drawn with arrows above them. Note that the friction force points in the direction opposite to the velocity vector.
The
figure at the right shows Newton's second law for this situation. The
three forces acting on the box are the applied force, the gravitational
force, and the ramp force. Their vector sum is the mass of the box times
its acceleration vector.
For the y component, the acceleration is zero because the box always stays on the ramp surface. The y component of the force by the ramp is renamed FN and is given a + sign, based on the top figure. The force of gravity has magnitude mg and negative y component, as shown. The applied force has magnitude FA and its y component is also negative.
These equations can be solved in various ways, depending on which parameters are known and which are unknown.