Inertia is the reason why people in cars need to wear seatbelts. A driver will continue the same speed as the car even though he/she will appear to be moving the same speed as the car. If the driver isn’t wearing a seatbelt, the driver will be thrown forward, smashing into the dashboard or through the windscreen. When wearing a seatbelt, the seatbelt stops inertia from keeping your body in motion when a car comes to a sudden stop. The force from the seatbelt is applied over a longer time, thus the force causes less damage.
States that the force that acts on an object depends on the mass and how fast it is moving.
The second law of motion applies to seatbelts. Without a seatbelt, the passenger’s acceleration with the car’s deceleration, increases the total acceleration. This is the reason why when a driver doesn’t wear a seatbelt and there is something in front, the driver flies forward and hits the object in front of him with a force that is the product of the mass and the acceleration of the object the driver is in. Using seatbelts can reduce the external force of an accident.