Which has a greater impact of force?

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Homework Help Overview

The discussion revolves around a physics problem comparing the impact forces experienced in two collision scenarios: one involving two identical cars colliding head-on and the other involving a car crashing into a stationary brick wall. The problem is situated within the context of inelastic collisions and impulse-momentum principles.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the concept of inelastic collisions and question whether the impact forces are the same in both scenarios. Some consider the implications of impulse and momentum, while others raise questions about the effect of relative motion during the collision.

Discussion Status

The discussion is active, with participants offering different perspectives on the problem. Some have suggested that the collision time is a critical factor, while others have referenced Newton's third law to argue that the forces should be equal. There is no explicit consensus, but various interpretations and considerations are being explored.

Contextual Notes

Participants note that the problem statement specifies the collision time is the same for both scenarios, which adds complexity to the analysis. There is also mention of the potential confusion that can arise from the problem's setup.

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Homework Statement


Consider two less-than-desirable options. In the first you are driving 30 miles/hr and crash head-on into an identical car also going 30 miles/hr. In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greatest impact force?


The Attempt at a Solution



Im thinking they are the same because both collisions are totally inelastic?
 
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would you rather run into a stationary wall or run into a wall moving towards you at 30 mph?
 
well, actually take a look at impulse ;] you can rewrite it as:
(change in momentum) = (Force) * (time of action)
change in momentum is the same for both cases, time is too, so...? ;]
 
housemartin said:
well, actually take a look at impulse ;] you can rewrite it as:
(change in momentum) = (Force) * (time of action)
change in momentum is the same for both cases, time is too, so...? ;]

wouldn't your time of impact be halved by the fact that the other car is moving towards you as well?
 
it is more complicated in real life i guess, but here problem statement said: "the collision time is the same in both cases"
EDIT: besides you can use Newton's third law here: action equals reaction. So the car will extend same force on other identical car or standing wall.
 
Last edited:
housemartin said:
it is more complicated in real life i guess, but here problem statement said: "the collision time is the same in both cases"

right you are, I apologize. Although that's a stupid question, usually physics teachers use the student's intuition for their benefit, not to confuse them.
 

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