Conservation of Momentum

Also known as: momentum conservation

principle

In a closed system with no external forces, total momentum before = total momentum after. Lets us predict the outcomes of collisions, explosions, and any interaction between objects.

💡 Intuition

Momentum can move between objects but can't be created or destroyed.

Core Idea

What one object loses in momentum, another gains — the total stays constant in a closed system.

🔬 Example

Two ice skaters push apart: one goes left, one goes right, total momentum stays zero.

🎯 Why It Matters

Lets us predict the outcomes of collisions, explosions, and any interaction between objects.

⚠️ Common Confusion

Only applies when external forces are negligible (or over very short times).

Related Concepts

Prerequisites

momentum impulse

Next Steps

elastic collision inelastic collision

How Conservation of Momentum Connects to Other Ideas

To understand conservation of momentum, you should first be comfortable with momentum and impulse. Once you have a solid grasp of conservation of momentum, you can move on to elastic collision and inelastic collision.

Go Deeper

Worked Examples

Step-by-step solved problems

Practice Problems

Test your understanding

Frequently Asked Questions

What is Conservation of Momentum in Physics?

In a closed system with no external forces, total momentum before = total momentum after.

Why is Conservation of Momentum important?

Lets us predict the outcomes of collisions, explosions, and any interaction between objects.

What do students usually get wrong about Conservation of Momentum?

Only applies when external forces are negligible (or over very short times).

What should I learn before Conservation of Momentum?

Before studying Conservation of Momentum, you should understand: momentum, impulse.

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