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# Momentum help? watch

1. So a few days ago, in my maths class I was doing a question on momentum which involved multiple collisions of 3 particle in which no external forces were acting. We were given the speed of a particle and the velocity of a particle before the collsion after the second collision, and were also give the information that the particle combined after the collision. So me having though I had a deep understanding of the problem, through the conservation of momentum assumed the conservation of momentum used the momentum before the collision, and after the multiple collisions (knowing it is now one particle with same velocity) calculated the final velocity of the particles.

My two maths teachers (another teacher of mine just happened to be there) argued that the method I used was wrong and that I had to separate the problem collsion by collision. I got the same both ways for which they argued it was just a coincidence the answer was the same. Who's in the right and wrong here? And help would be appreciated.
So a few days ago, in my maths class I was doing a question on momentum which involved multiple collisions or 3 particle in which no external forces were acting. We were given the speed of a particle and the velocity of a particle before the collsion after the second collision, and were also give the information that the particle combined after the collision. So me having though I had a deep understanding of the problem, through the conservation of momentum assumed the conservation of momentum used the momentum before the collision, and after the multiple collisions (knowing it is now one particle with same velocity) calculated the final velocity of the particles.

My two maths teachers (another teacher of mine just happened to be there) argued that the method I used was wrong and that I had to separate the problem collsion by collision. I got the same both ways for which they argued it was just a coincidence the answer was the same. Who's in the right and wrong here? And help would be appreciated.
At first read it sounds like your method is okay but it's really hard to say unless you provide the question.

Are you able to post the question or come up with a question similar and show us your working?
3. So if I've understood correctly:

1. You solved a problem which you haven't shown us using a method that you haven't shown us.

2. Your teachers solved the same problem using a different method that you haven't shown us.

3. You want us to tell you which method is correct.

Fair summary?

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Updated: February 5, 2017
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