An object of mass m slides down an incline with angle 0.

B)

FN - mgcosФ = 0

Given the mass of an object, forces that will be acting on it are as following

Force due to gravity = -mgcosΔ

Normal force = fN

Frictional force = -f

force applied forward = mgsinΔ

Horizontal force = mgsinΔ - f

vertical force = fN -  mgcosΔ

B).

Explanation:

As we know that the force on the mass "m" which slides along the inclined plane is along the inclined surface

So it must have accelerated along that surface only

So we can write the equation for force along the inclined plane as

now if we wish to find net force perpendicular to the plane then we can say that it must be zero

Because perpendicular to the plane the net force on the given mass must be zero as it is not accelerating along that direction

So here we can say

so we have

the answer for apex is the lowest

option number c is the right answer.