Car Crash: Wall vs. Identical Vehicle - Which Does More Damage?

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Discussion Overview

The discussion centers on the comparative damage caused by a car crash into a concrete wall versus a head-on collision between two identical vehicles, both traveling at 40 km/h. Participants explore the implications of momentum, relative velocity, and the physical characteristics of vehicles in the context of this scenario.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that both scenarios result in equal damage, but questions whether the vehicle hitting the wall experiences momentum loss due to recoil, depending on the car's construction.
  • Another participant references a source claiming that hitting a fixed object results in less damage than colliding with another vehicle, due to the relative velocity being higher in the latter case.
  • A participant challenges the quoted explanation, stating that while relative momentum is doubled in a collision with another vehicle, the momentum is shared between the two cars, potentially leading to different damage outcomes.
  • One participant expresses frustration over the repetition of the topic, indicating that similar discussions have occurred recently.
  • A moderator reminds participants to avoid starting new threads on the same topic and to respond to existing discussions instead.

Areas of Agreement / Disagreement

Participants express differing views on the damage outcomes of the two scenarios, with no consensus reached. Some support the idea that hitting a wall is less damaging, while others argue about the implications of momentum transfer in collisions between vehicles.

Contextual Notes

Participants reference external sources and previous discussions, indicating a complex interplay of ideas and assumptions regarding momentum and damage in collisions. The discussion remains unresolved with respect to the validity of the claims made.

Who May Find This Useful

This discussion may be of interest to those studying physics, particularly in the areas of mechanics and collision dynamics, as well as individuals curious about automotive safety and accident analysis.

Shane
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okay bringing up an old topic but

a car (lets just say 2000 kg) drives into a concrete wall (essentially immovable) at 40 km/h.
the same vehicle (make and model not the product of the colliision!) drives head on into another identical vehicle traveling in the opposite direction; both at 40 km/h.

Which does more damage?

They are equal no? Argue me if I am wrong but also couldn't you argue that the vehicle crashing into the wall has momentum lost to recoil, rolling away from the wall after it has hit? All of course depending on the construction of the car right? those cars in demolition derbies are built (impracticably for the transfer of momentum and safety's sake) to withstand heavy blows, so couldn't that vehicle lose some momentum to recoil on colliding with the wall?
 
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Also quoting this website: http://www.sciam.com/askexpert_question.cfm?articleID=00042194-68C4-1C71-9EB7809EC588F2D7

"You will do less damage to your car and yourself by hitting a fixed object. The reason is that the damage done is a function of the relative velocity of the objects. If you are traveling at 35 miles per hour and hit a large tree, the relative velocity is 35 miles per hour. However, if you hit a car coming toward you at 35 miles per hour, the relative velocity is twice that. The effect of hitting the other car is therefore roughly the same as of driving into the tree at 70 miles per hour."

Is that true? I had an extremely long argument with my physics teacher agreeing with the above quotation, but my physics teacher argued that even though the relative momentum is twice as much, there are two cars and the momentum is transferred as such with each vehicle taking half of the momentum during the crash.
 
I swear we had this same thread twice in the last two months. Why don't you do a google search for it? Hell, I did it for you. https://www.physicsforums.com/showthread.php?t=97485 There's one.

Did you read the next two paragraphs of the Scientific American link. The next two said why your quoted explanation was wrong.
 
Please do NOT start the same thread again! Respond to the existing thread that you have started already. Multiposting of the same topic is not allowed on PF.

Zz.
 

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