Final answer:
An un-seat-belted driver collides with the steering wheel because of inertia, which keeps the body moving at the initial speed of the car until it hits the steering wheel. The force experienced by the driver during a collision can be calculated using impulse. Safety features like airbags and seat belts reduce the force on occupants by increasing the collision time.
Step-by-step explanation:
An un-seat-belted driver collides with the steering wheel during a head-on collision because of inertia. The driver's body continues to move forward at the original speed of the car due to its inertia until it is acted upon by an external force, in this case, the steering wheel. This is based on Newton's first law of motion, which states that an object in motion continues in its state of motion unless acted upon by an external force.
The average force the driver experiences during a collision can be determined using the concept of impulse, which is the product of the net force and the time over which the force acts. Impulse equals the change in momentum, and since the driver's initial momentum is nonzero (due to the car's motion) and final momentum is zero (after coming to a stop), the impulse equals the initial momentum of the driver. If the driver's collision time with the steering wheel is about 0.20 seconds, then the force experienced by the driver can be calculated using the formula: force = change in momentum / time. Given a longer time to decelerate, such as with an airbag, the force experienced by the driver is much lower.
Safety features like airbags and seat belts are crucial because they increase the collision time which reduces the force on the driver, thereby preventing serious injuries during collisions. Cars are also designed to crumple upon impact, increasing collision time and reducing the forces felt by occupants.