Calculating momentum

A moving object has momentum. This is the tendency of the object to keep moving in the same direction. It is difficult to change the direction of movement of an object with a lot of momentum.

Momentum can be calculated using this equation:

p = m × v


p is the momentum in kilograms metres per second, kg m/s

m is the mass in kilograms, kg

v is the velocity in m/s

For example, what is the momentum of a 5 kg object moving with a velocity of 2 m/s?

momentum = 5 × 2 = 10 kg m/s


Notice that momentum does not just depend on the object’s mass and speed. Velocity is speed in a particular direction, so the momentum of an object also depends on the direction of travel. This means that the momentum of an object can change if:

  • the object speeds up or slows down
  • the object changes direction