Newton's laws of motion help explain why an object needs a force to make it move - inertia also explains this. Momentum, on the other hand, explains some of the most important interactions in nature.

Momentum is the product of mass and velocity. Momentum is also a vector quantity - this means it has both a magnitude and an associated direction.

For example, an elephant has no momentum when it is standing still. When it begins to walk, it will have momentum in the same direction as it is travelling. The faster the elephant walks, the larger its momentum will be.

Momentum can be calculated using the equation:

momentum = mass × velocity

p = m v

This is when:

- momentum (p) is measured in kilogram metres per second (kg m/s)
- mass (m) is measured in kilograms (kg)
- velocity (v) is measured in metres per second (m/s)

A lorry has a mass of 7,500 kg. It travels south at a speed of 25 m/s. Calculate the momentum of the lorry.

- Question
An ice skater has a mass of 60 kg and travels at a speed of 15 m/s. Calculate the momentum of the skater.