Momentum in Collisions and Explosions

This lesson covers momentum, the conservation of momentum, and how these concepts apply to collisions and explosions — as required by the Edexcel GCSE Physics specification (1PH0), Topic 2: Motion and Forces. You also need to understand how momentum concepts relate to vehicle safety features.

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What Is Momentum?

Momentum is a measure of how much motion an object has. It depends on both the mass and velocity of the object.

Momentum = Mass × Velocity

p = m × v

Quantity	Symbol	Unit
Momentum	p	Kilogram metres per second (kg m/s)
Mass	m	Kilograms (kg)
Velocity	v	Metres per second (m/s)

Key Points

• Momentum is a vector quantity — it has both magnitude and direction.
• The direction of the momentum is the same as the direction of the velocity.
• A stationary object has zero momentum (v = 0).
• A heavier object moving at the same speed has more momentum.
• A faster object of the same mass has more momentum.

Worked Example 1