Answer: This is because of inertia
Explanation:
What is inertia?
According to Isaac Newton Inertia is a force that resist change brought by an external force into a standing body or object it resist this change in an opposite direction .
Unless an outside force is applied on an abject it will maintain its constant velocity .
Inertia of that object is equal to its mass.
One can observe how far the object resist the opposite force and how far it's accelerate can determine its mass.
Inertia causes your body to move forward when the collision occur as the car breaks or step back you will be pushed forward.
