Answer: A person with no seatbelt will fly out because of the "Momentum" gathered from the speed of the car.
Example: Let's say there's a fast-moving object and there's an object inside, let's also say that the moving object is moving very fast. The fast-moving item is then forced into a complete stop and the item inside if not secured will fly out because of the momentum of the first item that suddenly came to a stop.
This is the best example I could give so yes, Good luck!
