How Do You Solve Momentum and Collision Problems in Physics?

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Homework Help Overview

The discussion revolves around solving a physics problem related to momentum and collisions, specifically involving a block and a wedge. Participants are exploring the principles of conservation of momentum and energy in this context.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the initial and final momentum of the system, questioning how to apply conservation of momentum. There are attempts to calculate the momentum before and after the block is released, and some participants suggest using conservation of energy for further analysis.

Discussion Status

Some participants have provided calculations and insights regarding the momentum values, while others are seeking clarification on the application of conservation laws. There is an ongoing exploration of how to proceed with the problem, particularly regarding the use of energy conservation.

Contextual Notes

Participants are working within the constraints of a homework assignment, which may limit the information shared and the methods discussed. There is a focus on understanding the underlying principles rather than arriving at a complete solution.

mike305
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Need help solving this problem
http://img409.imageshack.us/img409/5854/chp851yx1.jpg

Thank you
 
Last edited by a moderator:
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Hi, and welcome to PF. Please give your thoughts on the question, before we can help. Better still, use the posting template with which you were provided!
 
What is the momentum before the block is released? How about after? Then you can use energy for the second part
 
the momentum before the release is 0, and after is 2. I understand that i need to apply conservation of momentum in this problem somehow, but I don't see a way so far.
 
mike305 said:
the momentum before the release is 0, and after is 2. I understand that i need to apply conservation of momentum in this problem somehow, but I don't see a way so far.

Conservation of mmtm states that mmtm before=mmtm after. Think of the total system. Before the block starts moving, like you said, pi=0. When the block hits the horizontal surface, the total momentum pf= 0.5*4-v2*m2. (The negative sign appears, since the block moves to the left.) From this you can find the velocity of the wedge.

Can you carry on from here?
 
Last edited:
v2 = 2/3 m/s ( to the left) ?

and for part b, should I use convservation of energy (potential and kinetic) in order to find the height?
 
mike305 said:
v2 = 2/3 m/s ( to the left) ?

and for part b, should I use convservation of energy (potential and kinetic) in order to find the height?


I've not checked you calculation, but yes, it's to the left.

For b, as you say, you should use conservation of energy.
 
thank you very much for your help :smile:
 
mike305 said:
thank you very much for your help :smile:

You're very welcome! :smile:
 

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