Newton's First Law of Motion: Inertia
Sir Isaac Newton was an English mathematician, physicist, astronomer, theologian, as well as writer that is commonly identified as one of the most influential scientists of all time. Newton's shaped the way we understand motion along with the universe as a whole.
Newton's First Law of Motion is the law of inertia. Inertia is an objects tendency to maintain it's state of motion. So if it's at rest, it will stay at rest and if in motion it will stay in that constant state of motion. This occurs unless acted upon by an outside force.
Static Equilibrium is a state of being at rest
Dynamic equilibrium is the state of being in constant motion
Inertia makes your body want to keep going forward when in the car and you hit the breaks. Because of this your body leans forward.
Inertia and Mass are Directly Related
Inertia is directly related to an objects mass. A 80 kg human has a whole lot less inertia than a 3000 kg elephant.
The elephant takes a lot more force to start or stop moving.