Momentum is a property of an object's motion. When a push or a pull (a force) acts on an object and changes its motion, the quantity that gets changed is momentum. Energy is required to change the magnitude (size) of momentum, but not its direction.[1] Specifically, momentum (written as [math]p[/math]) is the mass of the object times its velocity (or speed with direction):[2]


Massive objects have more momentum for a given speed, while lighter objects have less momentum. This is why it takes more effort (force) to stop a fully loaded truck than an empty one. Likewise, faster moving objects have more momentum than slower moving objects.

One way to express kinetic energy is in terms of momentum ([math]p[/math]):

[math]KE = \frac{p^2}{2m}[/math]

Momentum is an important physics concept, to learn more about momentum please see hyperphysics.

Phet Simulation

The University of Colorado has graciously allowed us to use the following Phet simulation. Explore this simulation to see how momentum is transferred in collisions along with energy:

For Further Reading

For further information please see the related pages below:


  1. R. D. Knight, "Impulse and momentum" in Physics for Scientists and Engineers: A Strategic Approach, 3nd ed. San Francisco, U.S.A.: Pearson Addison-Wesley, 2008, ch.9, sec 1, pp. 242.
  2. There are corrections to this expression when the object is going near the speed of light, see hyperphysics for more details

Authors and Editors

Bethel Afework, Jordan Hanania, Kailyn Stenhouse, Jason Donev
Last updated: May 18, 2018
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