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+--- Thread: Conservation of Momentum — Why Rockets Work (/showthread.php?tid=427)
Conservation of Momentum — Why Rockets Work - Leejohnston - 01-08-2026
## Conservation of Momentum — Why Rockets Work
### 1. The Equation
Total momentum before = total momentum after
p = mv
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### 2. What Each Symbol Means
- p = momentum
- m = mass
- v = velocity
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### 3. What the Equation Is Telling Us
Momentum is conserved in an isolated system.
If something moves one way, something else must move the other way.
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### 4. Where It Comes From (Intuition)
Motion doesn’t disappear — it is redistributed.
Throwing mass backward pushes you forward.
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### 5. Worked Example
A rocket ejects exhaust backward →
the rocket gains forward momentum.
No air is required.
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### 6. Real-World Applications
- Rocket propulsion
- Collisions
- Recoil
- Space manoeuvres
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### 7. Common Misconceptions
- Rockets push on air → false
- Momentum and energy are the same → false
- Heavier exhaust always helps → false
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### Try It Yourself
Why does stepping off a boat push it backward?