Answer:
Newton's first law of motion or law of inertia
Explanation:
According to newton's first law, the law of inertia states that everybody continues its state of rest or of uniform motion in a straight line unless an uncompromised force acts on it.
When a high-speed moving car is abruptly stopped, a person sitting inside the car without wearing a seat belt continue to move forward.
Since the law of inertia opposes the state of the body which was in motion. The person would collide with the objects in his front and may cause injury.
So, while wearing a seat belt, this motion can be stopped as the person is attached to the seat. This reduces the impact and it is a safety measure.