gravity along a ramp physics question

Question

A shoe sits on a ramp without moving. As the angle of the ramp is increased, the shoe starts to move. This is because:

a) the normal force has increased

b) the coefficient of static friction has decreased

c) force of gravity on the shoe has increased

d)the component of the normal force along the ramp has increased

e) the component of gravity acting along the plane of the ramp has increased

Answer 1

I am not happy about using the components of forces in this case. The reason is simple: in reality there are only 3 forces acting on the body in this case:

W = mg - weight of the body, directed vertically down,

N - normal reaction force, directed perpendicular to the surface,

f_s - static friction force, directed against relative motion of the body.

When tan of the angle of the ramp becomes equal to the coefficient of static friction, the body starts to slide.

Please do not talk about forces that do not exist!