^Normal reaction, N
Reaction of net pressing force acting at right angles to the two contact surfaces is called normal reaction.
A pen is resting on a horizontal desk
The force of gravity is pulling down on it, but since it is at rest, it must also be experiencing a force of the desk pushing upward. This force is the normal force, thus N = W.
A body at rest on an inclined surface.
N = mg cos θ
A body pulled up with a force ‘F’ at an angle α to plane.
N = W cosθ – F sin α
A force ‘F’ pressing
a body against a vertical wall.
N = F