He is still in the air as the kick is being delivered. The fact that he allows his entire body mass to smash into the target before touching down and diverting all the energy into the target. As long as you are grounded there is still some energy left in the supporting leg.
Well, sure. I've already conceded jumping MAY allow you to move more of your mass into the kick if your technique is good. And mass is indeed one component of power, but it cannot be the only factor considered in isolation.
But do you see the point I am making? Foster's kick was devastating because it is an advanced manifestation of 'normal' technique. He is not jumping up, spinning 180 degrees, and then kicking. Notice also that he didn't pick the jump spinning back kick or the flying side kick for his attempt when he had the entire universe of kicks available to him per the scenario. Instead he went with the humble back leg roundhouse kick.
No we are not rockets and gravity slows down everything. As does friction. However the kick is still using the energy force provided by the muscles. removing the pulling force by jumping and kicking while at zero gravity (actually negative gravity while still going up) you enhance the speed and actually do speed up. Plus with the pull of gravity at impact your force is also increased.
I'm not convinced. I think the physics involved is considerably more complex with things like drag and propulsion and acceleration forces unaccounted. Also, the various kicks have different directional flow (rotation direction and force) which have to be considered as well, i.e. is an aerial 180 degree kick as powerful as its grounded cousin vs. the different comparison of a 360 or even a reverse 180 from the back side. Human muscle groups are distinct after all - it's not the same level of complexity as an abstract problem like shooting something straight up in the air and then measuring its rate of descent.
But science aside, logic would only dictate that if jumping or spinning did not increase power or speed then why do it.
Lets look at Olympic javelin throwers. They run then hop while throwing. I would have to ask why.
Olympic shot put tossers as well. They spin then hop and toss. There is added power and speed that is created with the spin and the hop.
They are projecting an object out of their hands much like a catapult does. They are building up momentum which will help with the velocity of the much smaller object which is leaving their hand. A somewhat different premise than using the muscles in the legs to launch and propel the entire body both UP and OUT towards a target, I would think.
I play tennis at a high level. When you turn on the tv and watch players serving the ball to start the point, it can look like they are jumping at the ball. They are not. They are initiating a kinetic chain from bending and then uncoiling their knees and then turning their hips, waists, and shoulders along with some wrist pronation. Like Bren Foster's kick above, the power from their natural motion carries them into the air, not because they thought deliberately jumping up was a good idea.
I know I'm not going to convince you, ATC, but I would suggest to anyone who is interested in discovering the power of jump kicks for themselves to take my suggested trial. Get a good kicker around your same size. Actually, even someone a bit smaller than you should be fine too since we're seeking to prove the idea that a jumping kick is powerful. Set up in a front stance without the back leg locked with a kicking shield in hand. Have the kicker take a running start and let them kick your shield with the intention to blast you if they can. Time yourself and when their kick is arriving, stick your front stance with your own hip power and thrust the shield against the kick with both arms. I know that when I have tried this, I have knocked back the kicker every time and yes, we can kick a bit.
