Forces are quantitative descrpitions of interactions of bodies that either push each other away or pull closer toghether. The magnitude of pulling or pushing is expresseed in terms of a quantity know as *Newtons* abbreviated as *N*.

According to Isaac Newton, there are three fundamental laws regarding forces:

1. At equilibrium the sum of all forces equal to zero: **ΣF = 0**

2. An external force acting on a body will accelerate the body at the same direction(vector) of the force. Thus, the sum of all forces is the product of the mass and the acceleration: **ΣF = ma**.

3. If a body **a** excerts a force on body **b**, then body **b** will excert the same amount of force on body **a**: **Fa = Fb**.