Calculating Momentum

Momentum is a property of moving objects, which can be defined using the equation:

  • p = Momentum in kilogram metres per second (kg m/s)
  • m = Mass in kilograms (kg)
  • v = Velocity in metres per second (m/s)

This equation shows three things:

1. An increase in mass leads to an increase in momentum.

2. An increase in velocity leads to an increase in momentum.

3. An object at rest (velocity = 0), will have no momentum.

Velocity

The momentum of an object does not just depend on an object’s mass and speed. Velocity (speed in a given direction) is a vector quantity, so the momentum also depends on the object’s direction of travel.

  • The momentum can change if the object changes direction.

As momentum depends on the object’s direction of travel, it can be a positive or negative value. If an object travelling in one direction has positive momentum, an object travelling in the opposite direction will have negative momentum.