Ablock lies on a plane raised an angle θ from the horizontal. three forces act upon the block: f⃗ w, the force of gravity; f⃗ n, the normal force; and f⃗ f, the force of friction. the coefficient of friction is large enough to prevent the block from sliding

YFy = 0 = Ffsinθ + Fncosθ - Fw

Explanation:

From the base of the vector Fn, draw a vertical line. the small angle between this line and Fn is also theta. The component of Fn in the vertical direction is Fncos(theta).

Take a moment to picture extreme cases. Sine is 0 at 0 and 1 at 90. Cosine is 1 at 0 and 0 at 90.

Tilt the incline so that the box is on a flat surface. How much of the gravitational force is along the x direction of the floor.

the answer is b, have negligible mass