Problem in Perfectly Elastic Collision w/o given mass

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Homework Help Overview

The discussion revolves around a problem involving perfectly elastic collisions between two identical bodies moving towards each other with different velocities. The original poster seeks guidance on the appropriate formulas and concepts to apply, as the topic is not covered in their textbook.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the conservation of momentum and energy in elastic collisions, questioning what is conserved during the interaction. Some suggest moving to the center of mass frame to simplify calculations. Others express uncertainty about the implications of the term "elastic collision" and its significance.

Discussion Status

Several participants have offered insights into the nature of elastic collisions, with one suggesting that the bodies exchange velocities. However, there is no explicit consensus on the correct approach or final outcomes, and some participants are still exploring the definitions and implications of the problem.

Contextual Notes

There is a noted concern regarding the lack of coverage of elastic collisions in the original poster's textbook, which may limit their understanding of the topic. Additionally, some participants question the assumptions made about the masses of the bodies involved.

naiian02
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what formula/s should i use in this problem:

2 identical bodies move forward each other. One has a velocity of 4 m/s and the other has a velocity of 6 m/s assuming a perfeclty elastic collision. Find their velocities after collision






pls help me p. elastic col is not included in my book XD
 
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naiian02 said:
what formula/s should i use in this problem:

2 identical bodies move forward each other. One has a velocity of 4 m/s and the other has a velocity of 6 m/s assuming a perfeclty elastic collision. Find their velocities after collision
What's conserved?

pls help me p. elastic col is not included in my book
Kind of hard to believe that a book that doesn't cover elastic collisions would have a problem involving elastic collisions. What book are you using?
 
Ooh, these questions are really beautiful.

To make the math MUCH MUCH more simple, move your observer to the center of mass frame.
Try and come up with a SIMPLE expression dealing with the relative velocities of the two objects before and after colliding. You'll be surprised.
 
naaiin: Look in your text for the definition of an eleastic collision. Check the chapter with this problem, and look in the book's index.

Saying a collision is 'elastic' actually gives you a lot of information about it.
 
naiian02 said:
what formula/s should i use in this problem:

2 identical bodies move forward each other. One has a velocity of 4 m/s and the other has a velocity of 6 m/s assuming a perfeclty elastic collision. Find their velocities after collision






pls help me p. elastic col is not included in my book XD

m1u1 + m2u2 = m1v1 + m2v2

its wad I've been taught in my school...
2 identical bodies means both object is the same...
assuming both objects have the same mass...
in a perfect elastic collision, both objects exchange velocity...
so the 1 that has 4ms-1 now has -6ms-1 while the 2nd 1 will be having 4ms-1
i'm not 100% sure of this though...do correct mii if any1 sees flaw in my statement...
 
cyy91 said:
m1u1 + m2u2 = m1v1 + m2v2

its wad I've been taught in my school...
2 identical bodies means both object is the same...
assuming both objects have the same mass...
in a perfect elastic collision, both objects exchange velocity...
so the 1 that has 4ms-1 now has -6ms-1 while the 2nd 1 will be having 4ms-1
i'm not 100% sure of this though...do correct mii if any1 sees flaw in my statement...

It's true. Ignoring the time of the collision, it is as if they went "through" each-other. Unless you distinguished the two by coloring them, or some other method, you wouldn't know if there was a collision or if each just retained its velocity. :)

Try and prove this with considerations of energy, though. That's the key point of the exercise.
 

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