Angle of Incline: A Basic Physics Question

[KayleighK]

I have kind of a stupid question to ask, but its just something I really don't understand. So in pictures (like the one below) where an object is sitting on an inclined plane, why is it that the angle between the force of gravity and the incline plane is the same as the angle of the incline?


http://www.glenbrook.k12.il.us/gbssci/Phys/Class/vectors/u3l3e9.gif

I don't really have a strong math background so these little things confuse me. Thanks in advance for any help.

 

[Delphi51]

Take a look at this diagram, featuring a 30 degree angle.
http://en.wikiversity.org/wiki/Motion_in_two_dimensions#Inclined_Planes
To understand why the other angle is 30, you must use the fact that the sum of the angles in a triangle is 180 degrees and note the 60 degree angle in each triangle (in fact the 60 degree angle is common to the two triangles).

 

[Dr.D]

Try to visualize what would happen if the angle were to begin to approach zero, that is if the incline were to decrease towards zero. What angles in the force diagram would approach zero and which would approach a right angle?