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Further motion concepts – WJECCalculating momentum

Moving objects have momentum, and forces cause it to change. The total momentum in an explosion or collision is conserved and stays the same. Equations of motion apply to uniformly accelerated motion.

Part of Physics (Single Science)Forces, space and radioactivity

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.

\(\text{p} = {\text{m}}\times{\text{v}}\)

where

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

m is the in kilograms (kg)

v is the in metres per second (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

Direction

Notice that momentum does not only 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