Physics
posted by Jim .
A box weighing 215 N is placed on an inclined plane that makes a 55 degree angle with the horizontal. Compute the component of the gravitional force acting down the inclined plane.

F = 215*sin55 = 176.1 N.

Given: W=215 N, <=55*
Find: F (parallel)
Solution: sin(<)=opp/hyp
opp =sin(<)(hyp)
F (parallel)=sin(55*)(215 N)
F (parallel)=176.1 N
Gravity is the parallel force that you're solving for because it is the force that makes the box slide down the incline. It's the ycomponent of weight when drawn on a vector diagram, but it's even understandable as a component of weight because weight=mg. 
jujl