Momentum is a measure of how much motion an object has. It depends on both its mass and its velocity: momentum = mass × velocity, or p = m × v. Momentum is measured in kilogram metre per second, written kg m/s.
Velocity has a direction, so momentum is a vector quantity and points in the same direction as the velocity. An object at rest has zero momentum. A 1500 kg car moving at 20 m/s has a momentum of 1500 × 20 = 30000 kg m/s.
Doubling the mass or doubling the velocity doubles the momentum. The equation can be rearranged to find velocity, v = p ÷ m, or mass, m = p ÷ v.