How to Measure Average Kinetic Energy

A massive, fast moving object, such as a freight train, has extremely high kinetic energy.

Kinetic energy, or the energy created for motion, exists everywhere in the natural world. Anything that moves and has mass creates kinetic energy. Kinetic energy should not be confused with potential energy. It measures stored, unreleased energy in an object. From birds to cargo jets, kinetic energy is simply the work exerted by an object on its surroundings. With the proper equipment, a little arithmetic, and the proper equation, the kinetic energy of anything can be measured.

Things You'll Need

• Means of measuring mass
• Means of measuring velocity
• Calculator

Instructions

1. Find the mass of the given object. You will need to find the mass in terms in kilograms. Convert to this unit, if necessary. Finding the mass for a small object is fairly simple; place it on a scale, something found in nearly every laboratory. Measuring masses for larger objects is more difficult. If the mass of the object is unknown, use other variables such as density and volume to derive the mass. If the masses of certain parts of the object are known, the total mass can be found by adding each mass together.

2. Find the velocity of the object. Velocity must be in terms of meters per second. Changes in velocity must be considered. Velocity, unlike mass which is a constant, can easily change with time. For example, a car on roller coaster has the highest speed at the bottom of a hill. At the top of the hill, however, its speed is nearly zero meters per second. If the measured object's velocity changes, simply find its average velocity. This can be done by subtracting the final speed from the initial speed and assuming magnitude. Considering magnitude means that the resulting average speed must always be positive. If the measured average speed is negative, remove the negative sign.

3. Calculate average kinetic energy using the kinetic energy formula. Since mass is a constant and velocity has been averaged, there is no need to manipulate this formula at all. The formula for average speed is KE = 0.5 * m * v ^ 2. In this formula, "KE" represents kinetic energy in joules, "m" is a symbol for mass in kilograms, and "v" represents average velocity in meters per second.

Tips & Warnings

• Changing the mass an object has a direct linear effect on its kinetic energy. For instance, if the mass of the object is decreased by half, its kinetic energy will decrease by half as well. Velocity, on the other hand, is not exactly linear. Since it is raised to the second power, changes in velocity will affect kinetic energy to a much greater degree than mass does. For example, if the velocity of an object is doubled, its kinetic energy will quadruple.

References

• University of Alaska at Fairbanks, Department of Physics; Velocity and Kinetic Energy; David Newman
• Georgia State University; Hyperphysics: Kinetic Energy
• Thomas Jefferson High School for Science and Technology: What is Potential Energy?