✓ Sources checked · 10 September 2026 · View verification
Kinetic energy depends on motion in a chosen frame; potential energy depends on a system’s configuration and a chosen reference. A body can have both at the same time.
By Matan · Updated
Two useful mechanical expressions
For a classical particle, K = ½mv². Near Earth’s surface in approximately uniform gravity, ΔU = mgΔh. A linear spring stores ½kx² relative to its unstretched state. Potential energy is not restricted to objects at rest. [1]
Worked energy during a drop
A 0.50 kg ball starts from rest 2.0 m above a chosen zero height. With g = 9.8 m/s², initial U = 9.8 J. At height 0.80 m, U = 3.92 J and, neglecting drag, K = 5.88 J. Speed is √(2K/m) = 4.85 m/s. The sum remains 9.8 J throughout this ideal fall.
Why speed matters strongly
Doubling speed quadruples kinetic energy at the same mass. Doubling mass doubles it at the same speed. A frame moving with the ball gives a different kinetic energy, so always use one frame consistently.
What a bounce changes
Impact can temporarily store elastic energy and transfer energy into heating, sound and permanent deformation. An ideal perfectly elastic bounce can return to the original height; ordinary passive real bounces often return lower. “Never” would be too broad without specifying the collision and any extra energy source.
A model, not a measured ball
The calculation omits air resistance, spin and impact deformation. Including these requires additional terms or a different stage of the energy balance.
Continue learning
- Gravitational Potential Energy Equation
- Coefficient of Restitution
- The Law of Conservation of Energy
How this article was checked
Sources checked; calculations checked where shown. The definitions, model assumptions and main explanatory claims were cross-checked against the sources below. Worked-example arithmetic and units were checked separately. These examples are illustrative calculations, not experimental measurements.
Source cross-check and editing assisted by AI. No independent human scientific review is recorded for this revision. The check applies to the version dated 10 September 2026; it is not a guarantee that every possible interpretation is correct.
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Sources and further reading
- OpenStax: Mechanical energy — Mechanical energy.
- OpenStax: Collision energy — Collision energy.
Cite this article
Matan. “Potential and Kinetic Energy Explained.” Your Physicist. Originally published 2026-06-11; updated 2026-09-10. https://your-physicist.com/potential-and-kinetic-energy-explained/
Revision history
: Added a checked simultaneous kinetic/potential-energy example and qualified the universal lower-bounce claim. Added linked sources and a transparent verification record.
