Momentum and Conservation

This lesson covers the definition of momentum, the conservation of momentum in collisions, and how safety features use this principle, as required by the Edexcel GCSE Combined Science specification (1SC0). Momentum is a key concept that connects force, mass and velocity.

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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 the velocity of the object.

$p = mv$p=mv

where:

• p = momentum (kg m/s)
• m = mass (kg)
• v = velocity (m/s)

Momentum is a vector quantity — it has both magnitude and direction.

Worked Examples

Example 1: Calculate the momentum of a 1200 kg car travelling at 25 m/s.

$p = mv = 1200 \times 25 = 30\,000 \text{ kg m/s}$p=mv=1200×25=30000 kg m/s

Example 2: A 0.16 kg cricket ball has a momentum of 6.4 kg m/s. What is its velocity?

$v = \frac{p}{m} = \frac{6.4}{0.16} = 40 \text{ m/s}$v=mp​=0.166.4​=40 m/s

Example 3: A 0.5 kg ball travels at 8 m/s to the right. What is its momentum?

$p = 0.5 \times 8 = 4 \text{ kg m/s to the right}$p=0.5×8=4 kg m/s to the right