How to Calculate Average Kinetic Energy

The energy of motion and movement is defined as kinetic energy. Any object in motion has kinetic energy. Every time you move a muscle in your body, you are converting the stored potential energy of your muscle into the kinetic energy of the resulting movement. The motion of waves (sound and radiant energy such as light), electrons (electrical energy), atoms or molecules (thermal energy) and objects (translational energy) are all forms of kinetic energy. The most commonly used example of kinetic energy versus potential energy is a roller coaster. At the top of a roller coaster hill, the car has stored potential energy; as the car moves down the hill, this potential energy is converted into rapid movement- kinetic energy. Kinetic energy can be calculated if you know or can measure the mass and velocity of a given object. To calculate the kinetic energy in the simplest of forms--translational kinetic energy--the object must be moving in a straight line at a constant speed. If the object is rotating or not moving in a straight line, the kinetic energy may be calculated, but the calculation is more complex than the calculation of translational kinetic energy provided here.

Things You'll Need

• Calculator

Instructions

1. Obtain or measure the mass of the object whose kinetic energy you wish to calculate.

2. Obtain or measure the velocity of the object in Step 1. The object must be moving in a straight line at a constant speed. Average velocity can be calculated by dividing the change in distance of the object by the change in time, or v = ∆distance/∆time where ∆distance is the end distance minus the starting distance (d2-d1) and ∆time is the end time minus the start time (t2-t1).

3. Square the measured or obtained velocity of the object.

4. Multiply the mass of the object by the squared velocity.

5. 

   Multiply the number obtained in Step 4 by ½. This is the kinetic energy of the object.

Tips & Warnings

• The standard units (SI) for kinetic energy are Joules, or kilograms per meter per seconds squared (kg*m/s2). Any calculated kinetic energy not in Joules should be converted accordingly.

• The kinetic energy calculated using the above equation is also often referred to as the translational kinetic energy.

• The kinetic energy of rotating bodies cannot be calculated using the above equation.

• The object whose kinetic energy is being calculated must be moving in a straight line at a constant speed.

Resources

• Physics textbook explanation of kinetic energy