How to Calculate Kinetic Energy in Joules

Kinetic energy is defined as the energy of motion. An object that is in motion or moving has kinetic energy. For example, when you run, your body converts stored chemical potential energy from your muscles into the kinetic energy of moving your legs. Kinetic energy can occur in many forms, including the motion of sound or light waves, electrical energy, thermal energy and the movement of objects (translational energy). A common way to visualize the difference between kinetic energy and potential energy is imagine how a roller coaster works. While at the peak of a roller coaster hill, the car has stored potential energy. The moment that car begins to move down the hill, the potential energy is converted into kinetic energy.

Difficulty: Moderate

Instructions

Things You'll Need:

• Calculator

1. Determine the mass, in kilograms, for the given object.

2. Measure the velocity of the object in Step 1 (if it has not been provided for you). The object should move in a straight line with a speed that is constant. The average velocity of an object can be determined by dividing change in distance by change in time, or v = ∆distance/∆time, where ∆distance is the end distance in meters less the starting distance (d2-d1) and ∆time is the end time in seconds less the start time (t2-t1).

3. Square the velocity from Step 2.

4. Multiply the squared velocity from Step 3 by the mass from Step 1.

5. Multiply the result calculated in Step 4 by 0.5. This is the kinetic energy of the object, KE=1/2(m x v squared). The result will be in the standard units (SI) for kinetic energy are Joules, or kilograms per meter per seconds squared (kg*m/s2).

Tips & Warnings

• The kinetic energy determined using this method is also called translational kinetic energy.
• The kinetic energy of objects moving in anything other than a straight line cannot be calculated using this equation.
• Always double check your calculations before reporting your final answer.

Resources

• Explanation of Kinetic and Potential Energy