Why do trampolines bounce?
For grown-ups: the science
A trampoline bounces because its stretchy mat and springs push back after you land on them.
Landing transfers energy from a jumper's moving body into elastic deformation of the mat, springs, and frame. As these parts return toward their resting shapes, they exert an upward force and return much of that energy to the jumper. Air resistance and internal friction convert some energy to heat and sound, so the bounce height decreases unless the jumper adds energy by timing body movements.
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Transcript
Look at the springy mat under your feet. Why does a trampoline bounce you up?
When you land, the mat stretches down and the springs stretch too. Your moving body presses them like a squishy spring.
The stretched mat and springs push back toward their resting shape. That push sends you up into the air.
Each bounce gets a little smaller because air and rubbing use some of the motion. Soon, the trampoline and your body come to rest.
So trampolines bounce because their stretchy mat and springs push back after you land!