Captain America Would Need a Rocket to Power His Civil War Jump-Kick

Wednesday, 16 March 2016 - 1:22PM
Wednesday, 16 March 2016 - 1:22PM
In the international trailer for Captain America: Civil War, Steve Rogers does an awesome running jump-kick on top of a car. We've all been analyzing these trailers for Marvel Easter eggs and clues about the plot, but physics professor Rhett Allain analyzed this particular kick for its scientific accuracy. Surprisingly enough, he found that Captain America's powers aren't so much on the up-and-up, and that he would need a rocket or some other propeller in order to perform this stunt.

Captain America: Civil War

In order to perform his analysis, Allain analyzed this clip from the trailer with a program called Tracker Video Analysis software, which allowed him to approximate the velocity of Captain America before and after the kick, and the person he's kicking (referred to by Allain as "the dude") after the collision. He found that Cap's velocity was nearly the same before and after the kick, while "the dude" went flying, which doesn't conform to the laws of physics.

According to the principle of the conservation of energy, if there are no external forces (and Cap and dude's masses are approximately the same), then Cap should have an equal change in momentum to the dude, just in the opposite direction. Instead, he keeps going at the same speed in the same direction, which would only adhere to the laws of physics if Captain America had no mass (you can find the full calculations here).

Sometimes, superpowers can be a catch-all for scientific objections, but Captain America's powers aren't really supposed to break the laws of physics. He's just supposed to be a particularly strong guy, so there's no reason to think his super-kick wouldn't conform to the laws of physics. If anything, he should go even further in the opposite direction.

So assuming that Captain America has mass, in order to keep going in the same direction after a huge kick, he would need some external force to propel him forward:

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You can see that if momentum is conserved, Captain America should recoil back after the kick. The only way to fix this would be to have some external force pushing him forward during this kick-maybe like a rocket pushing him. OK, there is another explanation. Maybe the dude has a wire that pulls him back when Captain America kicks him.
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Science of Sci-Fi

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