Newton is known for his Laws of Motion. His first Law of Motion states that an object at rest tends to stay at rest just as an object in motion tends to stay in motion unless acted upon by an unbalanced force. A resting object, therefore, would have to be pushed or accelerated by an external force. Similarly, a moving object tends to keep moving in the same direction unless an opposing force comes to act upon it. Think of a front-end collision as an "unbalanced force" acting upon a moving object.