Final answer:
Objects are thrown forward in a car due to inertia, the tendency of an object to maintain its state of motion. The concept of impulse is fundamental in understanding how safety features like airbags work, by extending the time over which force acts to reduce the force's impact.
Step-by-step explanation:
When a car suddenly stops, the objects in the back seat are thrown forward due to inertia. Newton's First Law of Motion, often referred to as the law of inertia, states that an object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. In the case of a car stopping suddenly, the objects continue to move forward because their inertia maintains their state of motion, despite the car's deceleration.
Impulse is the product of the net force acting on an object and the time over which it acts (Fnet At). Understanding impulse is critical in vehicle safety design. For example, airbags provide a cushion that increases the time over which the force acts when reducing a person's momentum during a crash, thereby lessening the force and reducing the risk of injury. Similarly, modern cars are built with plastics and designs meant to crumple upon impact, which extends the collision time and consequently decreases the force experienced by the vehicle and its occupants.