The roof of this building is
constructed as a strongly tilted inclined plane to allow snow to slide off rather than
pile up and load the structure.
Although the force of gravity
acts straight down, when an object is supported by an inclined plane, components of its
weight exist both parallel () and
perpendicular () to the surface. It is
only possible for motion to take place on the incline at a inclined plane, and it is that drives that motion. influences friction on an inclined plane. The angle
between the line-of-action of the weight vector (Fg) and the normal to the
incline equals the
incline angle. Consequently,
Fg sin pushes the object down the incline,
cos pushes it into
the surface. The Second Law applies independently in each perpendicular direction.
As shown in the free-body diagram, there is a
force that will accelerate the object down the
slope. There is no acceleration perpendicular to the slope; net = maperpendicular =0, and must be balanced by an equal and oppositely directed
reaction force FN.