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Mission MC3 Impulse and Momentum Change Variables - Question Group 2 Help
Cars are equipped with crumple zones. In a front-end collision, these crumple zones are designed to intentionally fold up and crumple during the short duration of the collision. One way that a crumple zone enhances safety is by preventing the car from rebounding. Preventing rebounding protects the passengers because it _____.
When a force is exerted upon an object in a collision, the object is said to have encountered an impulse. The impulse is simply the mathematical product of the force exerted on the object and the amount of time over which it was exerted. The impulse changes the object's momentum and is equal to the amount of momentum change.
or
F•t = m•∆v
In a car collision, the momentum of the car is stopped (usually) by the action of a force for a given amount of time. To minimize the fatalities in such collisions, safety engineers use physics principles to design safety features that are incorporated into the cars. Crumple zones is one example of these safety features. By equipping the car with a crumple zone, the safety of a passenger is protected by reducing the force on the passenger. This is done in two ways - by increasing the time of collision and by preventing a rebound effect. This question pertains to the rebound effect.
Rebounding will cause a car to slow down, turn around, and be rebounded back in the opposite direction. This rebounding causes a velocity change that is greater than simply slowing down and stopping. So, by preventing rebounding, a crumple zone keeps the car's velocity change as low as possible. And because momentum change and impulse also depend upon velocity change, the incorporation of a crumple zone keeps these to a minimum as well. The car becomes all crumpled up (in fact, it's probably totaled), but the passengers walk away alive (we hope). Now that's physics for better living.
