Explanation:
Newton's second law of motion says that the net force on an object is equal to its mass times acceleration. For an object sliding on a flat surface, there are 3 forces acting on it: weight force mg pulling down, normal force N pushing up, and friction force F in the opposite direction of the motion.
In the vertical direction, the object is not accelerating, so we can show that the weight force and normal force are equal.
∑Fᵧ = maᵧ
N − mg = 0
N = mg
In the horizontal direction, the only force is friction. We can show that this is equal to the mass times acceleration.
∑Fₓ = maₓ
F = ma
Solving for acceleration:
a = F / m
