Final answer:
Newton's first law of motion, also known as the law of inertia, explains why wearing a seat belt is important in a car crash situation.
Step-by-step explanation:
In this situation, Newton's first law of motion directly applies. This law states that an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and in the same direction, unless acted upon by an external force. When a car suddenly stops in a crash, the passengers' bodies tend to stay in motion due to inertia, while the car comes to a sudden halt. Wearing a seat belt provides an external force that helps restrain the passenger's body, preventing it from moving forward.
Learn more about Newton's laws of motion and seat belt safety