Re the highly imperfect efficiency energy of a trampoline how is this stunt possible where the jumper he glides back onto the ledge he jumped from?
I didn’t watch the video, but the “it will never bounce as high as it started from” rule is for inanimate objects. People have legs, with muscles, that they can use to jump higher than they would ordinarily bounce. They can also jump into the trampoline so that they land with more force than gravity alone could give them.
For one thing, most of them aren’t *falling *off the ledge to start, they’re jumping. So they a) are above the ledge when they begin their descent and/or b) have more momentum than they would if they were simply falling off the edge. that alone is probably enough to give them enough momentum to return to their ‘starting point’.
Not to mention that a number of them “wall walk” up the wall under the ledge. That’s a little additional energy input.
Even when bouncing with their back against the trampoline canvas, they can still add energy to the bounce by timing the way they move their legs (in the same sort of way that you can use your legs to increase the height of your swing on a traditional seat swing)
This is why a guy on a trampoline alone can jump higher, and then higher still, and then higher yet. The sky (or ceiling) is the limit.
Lots and lots of kids find out how dangerous this is…