# Normal Force and Acceleration down the slope

## Homework Statement

2. Homework Equations + questions
1) Normal Force
when considering mg as the vertical force,
mg = N cos θ
however, when considering N as the vertical force,
N = mg cos θ
note: θ is the same due to opposite angle

which equation is correct?

2) Acceleration down the slope due to gravity (frictionless)
a = g sin θ
why can't I use the originally given θ?
e.g. sin θ = g/a
a = g/sin θ
why must I use the derived θ instead of the one between the horizontal and the inclined place?