A 3.9 kg bag of groceries is in equilibrium on an incline of angle θ = 70°. Find the normal force of the incline on the bag.
The normal force is the force opposite to the force of the bag on the incline, so the y-coordinate of the force. Just use trigonometry to calculate the force in the x and y directions, use a triangle. The hypotenuse is the mass times acceleration, the x and y components a fraction of this total force value.