Elastic Collisions between two objects

AI Thread Summary
The discussion centers on calculating the relative speed of two siblings after an elastic collision on ice. The 52 kg sibling is initially at rest, while the 60 kg brother skates towards them at -4.9 m/s. The participant is struggling to find the correct answer, having attempted 4.55 m/s but received feedback that it is incorrect. There is confusion regarding the application of the momentum conservation equation provided, which is noted as a trivial identity. The key focus is on determining the correct relative speed post-collision.
Flinze
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Homework Statement


You have an inertia of 52 kg and are standing at rest on an iced-over pond in your skates. Suddenly, your 60-kg brother skates in from the right with x component of velocity -4.9 m/s and collides elastically with you.

1. What is the siblings' relative speed after the collision?

Homework Equations


m1v1+m2v2=m1v1+m2v2

The Attempt at a Solution


WvlUmrX.png

This is part of my assignment online, and it when I plug in 4.55 m/s it says my answer is incorrect. I'm lost at this point.
Thanks in advance!
 
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Flinze said:

Homework Statement


You have an inertia of 52 kg and are standing at rest on an iced-over pond in your skates. Suddenly, your 60-kg brother skates in from the right with x component of velocity -4.9 m/s and collides elastically with you.

1. What is the siblings' relative speed after the collision?

Homework Equations


m1v1+m2v2=m1v1+m2v2
Has the above equation any information? It is a trivial identity.

Flinze said:

The Attempt at a Solution


WvlUmrX.png

This is part of my assignment online, and it when I plug in 4.55 m/s it says my answer is incorrect. I'm lost at this point.
Thanks in advance!
Relative with respect what?
The question is the relative speed of you and your brother after the collision.
 

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