This is another item of the sport that come directly from skateboarding. Here is a good example: take a normal size 6" sidewalk, and as your rolling along, do your best ollie, say u can do 2 cinderblocks. Now take that sidewalk and give it a smooth driveway cut in the middle of it so that it looks like a very shallow (only 6"!!) halfpipe. Using the same physics described by the first responder and also what the guy in the SA vid is doing, you can now set up a 3 1/2 foot warning sign at the top of one or both transitions and boost ollies like you never knew you could.
Maybe moot point, maybe ur not a skater, but the sensation and results when you do it right are the exact same.
Timing is everything.
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