bullet2 Calculating Momentum

bullet3 Definition of Momentum

Momentum  is the product of an object's velocity and its mass.
If you compare the motion of a car and a child's bicycle you can see how an object's mass contributes to momentum.  A car has a much greater mass than a bicycle, so if they were both moving at 10m/s, then the momentum of the car would be greater.  

Let's look at the equation for momentum.

  • Momentum Equation
    momentum = mass x velocity   or   
    p = mv

    •    The SI unit for mass is kg.
    • The SI unit for velocity is m/s.
    • The SI unit for momentum is kg x m/s.

    The answer to any momentum problem not only has an SI unit, but also a direction.  An object's momentum is in the same direction as its velocity.

    If you need to review solving one step multiplication problems, click below.

    See also: Solving One Step Multiplication Problems
    • Steps for Solving Momentum Problems
      As in the procedure for solving other force problems,  calculating momentum is a step by step process.  We will use a problem to work through the steps.

      Problem:  Calculate the momentum of a 11.35kg wagon rolling down a hill at 12m/s.

      Step 1 :  Write down the equation needed for solving momentum.
      p = mv

      Step 2:   Insert all known measurements into the formula.
      p = (11.35kg) (12m/s)

      Step 3:  Solve.  Carefully enter all numerical values into your calculator.
      p = 136.2 kg x m/s down the hill

      • Check your work and make sure that all numbers have a SI unit label and that you have the correct SI unit for momentum.  
      • Don't forget the direction in your answer label!  The velocity is down the hill, so the momentum will be the same.
      • It is a good idea to always double check your answers because it is very easy to hit the wrong button on your calculator!

      Go get some momentum formula experience!  Do the practice problems.

      • Momentum Practice Problems
        Follow the same steps you just learned and don't forget to label your numbers.


        1.  Calculate the momentum of a 0.15 kg ball that is moving toward home plate at a velocity of 40m/s.

        2.  Which has greater momentum, a 2.0kg hockey puck moving east at 2.5m/s or a 1.3kg hockey puck moving south at 3.0m/s?

        3.  A track athlete throws a 2kg discus into a field with a velocity of 21m/s.  What is the momentum of the discus?

        4.  Calculate the momentum of a 700g ball that is rolling down a ramp at 4.6m/s.

        5.  A cannon fires a 40.5kg shell toward a target and the shell moves with a velocity of 120m/s.  Calculate the shell's momentum.

        Feeling pretty good about your abilities?  Try some of the momentum links!


bullet3 Links



Here are some links to go and find out more about momentum:

1.  How about a review  of momentum?