Final answer:
The impulse-momentum theorem is used by highway safety engineers to determine collision forces, which is vital for designing safety features in vehicles and understanding the physics of car accidents.
Step-by-step explanation:
Highway safety engineers use the impulse-momentum theorem primarily to determine collision forces during an accident. The impulse-momentum theorem relates the impulse, which is the net force exerted on an object times the duration of the impact, to the change in momentum of the object.
For example, in a car crash scenario, knowing the velocity of the car just before impact and the duration of the collision helps engineers estimate the average force exerted by a barrier on the car. Similarly, to calculate the stopping distance, the duration of the driver's reaction time and the distance traveled during this time are considered, underscoring the application of the impulse-momentum theorem in automobile safety.