When you land on a trampoline, the mat and springs stretch. Your kinetic energy is transferred into an elastic potential energy store. The stretched trampoline then exerts an upward force and transfers energy back to you as it returns towards its original shape. With good timing, you can add energy using your muscles on each bounce. Some energy is always dissipated as heating and sound, so the trampoline is not creating energy from nothing. The high jump comes from storing and returning energy efficiently while producing a large upward force over the right part of the motion.

You can spot the same idea in sport, transport and amusement rides. Designers predict how motion will change before building anything, because forces, momentum and energy affect comfort as well as safety. That is why seat belts, suspension, landing surfaces and ride restraints are physics applications, not just pieces of equipment.

The effect becomes clearer when it is reduced to measurable quantities: forces can change motion, energy is transferred between stores, and particles or fields provide a model for what cannot be seen directly. Those models let us predict what should happen when one variable changes, then test the prediction against observations or measurements.