Two Hockey Puck Collision: Calculating Speed After Impact

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Homework Help Overview

The problem involves a collision between two hockey pucks of equal mass, where one puck is initially at rest and the other is moving. The velocities after the collision are described in terms of angles relative to the initial velocity of the moving puck, raising questions about momentum conservation.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the conservation of momentum and its implications for the final velocities of the pucks. There is confusion regarding how the final momenta relate to the initial momentum, particularly in terms of vector direction.

Discussion Status

Some participants have attempted to visualize the problem using vector diagrams and the sine law, indicating a productive exploration of the concepts involved. However, there is still uncertainty about the application of momentum conservation in this context.

Contextual Notes

Participants mention an upcoming test, which may add urgency to their understanding of the problem. The original poster notes confusion about the conservation of momentum, suggesting that assumptions about the system's behavior are being questioned.

Morhas
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Homework Statement


Two hockey puck of equal mass undergo a collision on a hockey rink. One puck is initiall at rest while the other is moving with a speed of 5.4m/s. After the collision, the velocities of the pucks make angles of 33 and 46 (degrees) relative to the initial velocity of the moving puck. Determine the speed of each puck after the collision.


Homework Equations





The Attempt at a Solution



We have tried several failed approaches. The correct answer is 3m/s and 4m/s. What is confusing us is that the momentum should be conserved. So the sum of the two final momentums should be that of the initial momentum. Thanks in advance,
 
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Bump. Can anyone explain this? My friend and I have a test tommorow and we still don't see how this is possible. Thanks.
 
Morhas said:
Bump. Can anyone explain this? My friend and I have a test tommorow and we still don't see how this is possible. Thanks.
It is conserved. momentum is a vector quantity. The initial momentum is to the right. The final momentum, the vector sum of the 2 pucks after the collison, must be equal to and in the same direction as the initial momentum.
 
Ahhh I see. So What I've done is drawn the two vectors as two sides in a triangle, with the third side being the initial momentum vector. Then I solved with sin law. Thanks for the post!
 

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