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183_notes:collisions [2021/04/01 01:56] – [Momentum Conservation in One dimension] stumptyl | 183_notes:collisions [2021/04/01 01:59] (current) – [Sometimes, you can approximate that the system's momentum is conserved] stumptyl | ||
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One situation where the concept of a [[183_notes: | One situation where the concept of a [[183_notes: | ||
- | ==== Momentum is never conserved ==== | + | ====== Momentum is never conserved |
- | In real situations that you have observed in your everyday life, the momentum of a system is never conserved. There are always external interactions that act to change the system' | + | In real situations that you have observed in your everyday life, the momentum of a system is never conserved. There are always external interactions that act to change the system' |
Δ→psys=→psys,f−→psys,i=→FsurrΔt | Δ→psys=→psys,f−→psys,i=→FsurrΔt | ||
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What you will do is consider when the external interactions are small enough or occur over a short enough time where the impulse delivered by the system' | What you will do is consider when the external interactions are small enough or occur over a short enough time where the impulse delivered by the system' | ||
- | === Sometimes, you can approximate that the system' | + | ==== Sometimes, you can approximate that the system' |
[{{ 183_notes: | [{{ 183_notes: | ||
- | In some cases, the external interactions on the system can be neglected when compared to the internal interactions between particles in the system. Think of a system of two particles that are going to collide (Figure to the right). In this situation, the particles in the system exert huge contact forces on each other as compared to external interactions (gravitational force, air resistance, etc.). Moreover, the collision occurs over a very short time. In this situation, the impulse delivered by the surroundings can be neglected (→FsurrΔt≈0) because it's so small compared to the forces that the objects in the system experience due to each other. So, in this case, you have momentum conservation (to the extent we can say the external interactions don't really matter): | + | __In some cases, the external interactions on the system can be neglected when compared to the internal interactions between particles in the system.__ Think of a system of two particles that are going to collide (Figure to the right). In this situation, the particles in the system exert huge contact forces on each other as compared to external interactions (gravitational force, air resistance, etc.). Moreover, the collision occurs over a very short time. In this situation, the impulse delivered by the surroundings can be neglected (→FsurrΔt≈0) because it's so small compared to the forces that the objects in the system experience due to each other. So, in this case, you have momentum conservation (to the extent we can say the external interactions don't really matter): |
Δ→psys=→FsurrΔt≈0 | Δ→psys=→FsurrΔt≈0 |