Safer Collision: Front-end Damage vs. No Damage - Impulse-Momentum Theorem

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Homework Help Overview

The discussion revolves around the safety of car collisions, specifically comparing scenarios where a car's front end is crumpled versus one where no damage occurs but both cars bounce off each other. The Impulse-Momentum Theorem is referenced to analyze the implications of these scenarios on safety.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between impulse, momentum change, and the safety implications of different collision outcomes. Questions arise about the effectiveness of energy absorption in crumpled structures versus rigid ones.

Discussion Status

There is an ongoing exploration of the concepts, with some participants suggesting that the first scenario may be safer due to energy absorption. Others are questioning the assumptions behind the scenarios and considering the implications of momentum change.

Contextual Notes

Participants are discussing the implications of the Impulse-Momentum Theorem without reaching a definitive consensus on which scenario is ultimately safer. The conversation includes analogies to other situations involving force absorption.

pebbles
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[SOLVED] What would you say...

Which is safer, a collision in which the front end of a car is completely crumpled, or a collision in which no damage is done to the car, but the two cars bounce backwards off one another. Use the Impulse-Momentum Theorem.

Hm. Well, the Impulse-Momentum Thm. says that a faorce exerted over some time, impulse, causes a change in momentum. So, by increasing the time over which a force must act to stop motion, the force can be reduced and the potential damage reduced. So, the scenario that is safer...logically I'm thinking the second scenario, but I'm not really thinking as a physicist. I'm just thinking that if there's no damage, it has to be safer.
 
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Would you rather be riding in a car with a spring supported bumper, or one with a rigid 'no - give' bumper? Or if you jump from a building, is it better to land with legs stiff and erect, or bend your knees as you hit the ground?
 
pebbles said:
Which is safer, a collision in which the front end of a car is completely crumpled, or a collision in which no damage is done to the car, but the two cars bounce backwards off one another. Use the Impulse-Momentum Theorem.

Use the Impulse-Momentum Theorem

Think on this line: In which case change in momentum is more? Then, assuming time of impact to be same, you can calculate in which case impulse is more.
 
now that you put it that way, it seems to make more sense. so, the first scenario would be safer because the energy is absorbed by the front end of the car...
 
pebbles said:
now that you put it that way, it seems to make more sense. so, the first scenario would be safer because the energy is absorbed by the front end of the car...

It's why those barrels at the entry to a highway exit ramp are filled with sand (to go 'splash' on the occasion someone's car rams them), rather than a nice big synthetic rubber bumper...
 
ok. thanks everyone. it makes sense now.
i greatly appreciate it!
:]
 

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