Can Momentum Be Conserved in Different Collision Scenarios?

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Homework Help Overview

The discussion revolves around the concept of conservation of momentum in various collision scenarios involving two objects, A and B. The original poster explores different situations regarding their motion and interactions, questioning the validity of momentum conservation in each case.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster presents several scenarios regarding the motion of objects A and B during collisions, questioning whether momentum can be conserved in each case. They consider scenarios where A and B move in the same direction, opposite directions, and where one is stationary while the other is moving. They also express uncertainty about the situation where both are stationary.

Discussion Status

Some participants provide feedback on the original poster's reasoning, suggesting that while some scenarios are plausible, others may violate the principle of conservation of momentum. There is an indication that the discussion is ongoing, with participants exploring the implications of momentum conservation in different contexts.

Contextual Notes

The original poster's reasoning includes assumptions about mass and velocity relationships in collisions, and there is a mention of external forces being absent. The discussion also touches on the potential transformation of kinetic energy into other forms, raising questions about energy conservation in conjunction with momentum conservation.

Meowzers
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So, I am trying to grasp the concept of conservation of momentum. I need someone to just look over my reasonings (and correct me for any errors) for the following situation.

Let's say there are two objects, A and B. A is moving and then it has a head-on collision with object B, which is stationary. There are no external forces acting upon the objects. So, I'm trying to figure out which of the following situations are possible.

-A and B move in the same direction - I say this is possible if object A has a mass that is much greater than B. This way, when the objects collide, object A's velocity barely gets changed after colliding with B.

-A and B move in opposite directions - This is possible - I saw a lot of demonstrations showing this result.

-A moves and B is stationary - I think this is possible. It's like the reverse of the first situation. The mass of A is a lot smaller than B so that it just bounces off B.

-A is stationary and B moves - I think this is possible. Elastic collision? It's like that toy where you pull back one ball, and the one on the opposite end flies off at the same veleocity.

-A and B are both stationary - This one I'm not sure about. Isn't it possible that the KE turns into other forms of energy. But then, the conservation of energy formula wouldn't work.

m1v1 + m2(0) = m1(0) + m2(0)
m1v1 = 0. That means the ball either has no mass or no velocity, which wouldn't work for the problem.
 
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Your thinking is not bad when you say B could be stationary when A is much less massive than B, but in fact B has to move some. Even the Earth moves under you feet when you jump up and down.

The last one would violate conservation of momentum. The masses could stick together, with almost all the energy being lost, but even if they stick they both have to move.
 
Thank you very much for your help!
 
Meowzers said:
-A moves and B is stationary - I think this is possible. It's like the reverse of the first situation. The mass of A is a lot smaller than B so that it just bounces off B.

If A has momentum moving towards the right, hits B, and moves towards the left, what happened to its momentum?
 

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