bullet2 Calculating Force

Not only is the universe stranger than we imagine, it is stranger than we can imagine.
Sir Arthur Eddington (1882-1944)

bullet3 Definition of Force

Force   is a product of mass and acceleration.  

You have practiced acceleration problems and now we will look at determining the amount of force that is applied to objects in motion.

  • Force Equation
    The equation for is
    force = mass x acceleration     or    f = ma
    • The standard unit for mass is kg.
    • The standard unit for acceleration is m/s2.
    • The standard unit for force is newton (N).   A newton is a derived standard unit.  This means that the SI unit of newton is composed of two or more standard units.  1N = 1 kg x 1m/s2.

    Let's look at the steps for solving a force problem.
    If you need to review solving one step multiplication problems, click on link below.

    See also: Solving One Step Multiplication Problems
    • Steps for Solving Force Equation
      How much force must be applied to a toy car that has a mass of .25kg to achieve an acceleration of 2.4m/s2?

      Step 1:   Write down the formula needed to solve the problem.
      f = ma

      Step 2:   Place the known measurements into the formula.
      Known :  The mass of the car is .25kg and the acceleration of the car is 2.4m/s2.
      f = (.25kg) (2.4m/s2)

      Step 3:   Enter the numbers into your calculator and solve.
      f = .6N  A force of .6N must be applied to the toy car.

      • Make sure that all of your numbers in the equation have a SI unit and make sure you label your answer with the correct SI unit for force (N).  

      Now you can practice some problems on your own.

      • Force Practice Problems
        You will need to show all work set up in the equation.  Don't forget to label all numbers!

        1.  If a 4500 kg car is traveling westward with an acceleration of 35.2 m/s2, what is the force acting on it?

        2.  I am a roller skater with a mass of 72kg.  If I am accelerating toward a wall at 3.7m/s2, what will be the amount of force at which I hit the wall?  

        3.  A dock worker needs to stop a box of goods that is rolling across a manual conveyer belt.  The box has a mass of 8.35kg and is accelerating at .75m/s2.  How much force will he need to apply to the box in order to stop it?

        4.  How much force must be applied to move a 55kg ice skater to an acceleration of 12.5m/s2?


bullet3 Links

Ready to try some problems that will challange you?   Click here.

These problems are a bit tougher.  Try these!