When an object speeds up, something must be doing work on it â a force acting through a distance. The work done equals the gain in kinetic energy. This is the work-energy theorem.
When an object slows down, its kinetic energy must go somewhere. If it hits a wall, KE transfers to elastic PE (deformation) and then to thermal energy. If brakes are applied, KE transfers to thermal energy of the brake pads via friction. If it compresses a spring, KE transfers to elastic PE. Energy is always accounted for.
In a frictionless system, KE and GPE continuously exchange. A pendulum swings: maximum KE at the bottom, zero KE at the top â and maximum GPE at the top, zero GPE at the bottom. The sum (KE + GPE) remains constant throughout the swing. This is why physicists love the concept of conservation of energy as a problem-solving tool.
This how it works covers How It Works: KE and Conservation of Energy within Kinetic Energy for GCSE Physics. Revise Kinetic Energy in Energy for GCSE Physics with 15 exam-style questions and 30 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 5 of 15 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Kinetic Energy
Which of the following objects has kinetic energy stored in its kinetic energy store?
A car travels at 20 m/s. The driver then doubles their speed to 40 m/s. Explain what happens to the kinetic energy of the car and by what factor it changes.