Kinetic Energy
Kinetic energy is the energy an object has because of its motion, depending on its mass and speed squared.
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Kinetic energy is the energy an object has because of its motion, depending on its mass and speed squared.
- KE equals half m v squared
- Doubling speed quadruples KE
- Measured in joules
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Kinetic Energy?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Kinetic Energy. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Kinetic Energy in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Kinetic Energy explains how the physical world behaves, from sport and transport to electricity and medicine.
Kinetic Energy in detail
Kinetic energy is the energy an object has because of its motion: KE = ½mv². It depends on the square of the speed, so doubling the speed quadruples the kinetic energy, which is why high-speed crashes are far more dangerous and braking distances grow rapidly with speed.
The work done by the resultant force equals the change in kinetic energy. A 1,000 kg car at 20 m/s has 200,000 J of kinetic energy. This relationship is used to calculate stopping distances, speeds of falling objects and the energy of moving machinery.
How the interactive helps you understand Kinetic Energy
Watch the energy stores in the interactive. Use any sliders or buttons it offers to change the values and see how the energy stores responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Kinetic Energy.
Real-life uses and examples
- Predict what a ball, car or circuit will do with Kinetic Energy before you do the calculation.
- Explain everyday devices, such as brakes, lifts or chargers, using Kinetic Energy.
- Use Kinetic Energy to make sense of a practical and its results.
Common mistakes to avoid
- Mixing up Kinetic Energy with a related quantity that has different units.
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Kinetic Energy
What is Kinetic Energy?
Kinetic energy is the energy an object has because of its motion, depending on its mass and speed squared.
What are the most important points about Kinetic Energy?
The main points are: KE equals half m v squared; Doubling speed quadruples KE; Measured in joules.
Why is Kinetic Energy useful?
Understanding Kinetic Energy explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Kinetic Energy?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Kinetic Energy?
Related topics in Physics include Energy Efficiency, Simple Machines, Impulse and Collisions.