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If one had three humanly habitable planets with the same gravity but different atmospheric densities due to composition, namely

  • Earth,
  • one with a denser atmosphere (about 1.5x as dense)
  • one with a less dense atmosphere (about 0.75x as dense)

then how different would blunt force be for a person being punched/kicked/shoved/etc. on each planet? Assuming that person pushing/being pushed are doing this test on each planet, that is.

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    $\begingroup$ -1 for no research effort from your part. Sorry, but this is what was recommended to me $\endgroup$ – Raditz_35 Jun 20 '18 at 9:27
  • $\begingroup$ how is this going to happen? Acclimation plays a big role when changing environment. $\endgroup$ – L.Dutch Jun 20 '18 at 9:43
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    $\begingroup$ @Raditz_35 you know, if I had to research this, I would not know where to begin. It's not like people reenact MMA matches in pressure chambers for rhe sake of science. $\endgroup$ – Renan Jun 20 '18 at 9:48
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    $\begingroup$ @Renan How about providing numbers for the average force of a punch, speed of fall or just one example for a place with such a density. E.g. I believe 3/4 is pretty close to the density on Mt. Everest. Also, it might be trivial to you, but the effect that a high density would even have on objects moving through them or whatever the Op expects ... Currently one would have to start with a basic Physics education before one can answer this question. I could come up with many things that would've shown some effort put into this and given answers a place to start somewhere $\endgroup$ – Raditz_35 Jun 20 '18 at 9:59
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    $\begingroup$ @Renan PS: I've seen this many times before. If the OP provides absolutely nothing, everyone is going to talk about something different in their answer because nobody has any idea what the OP is aiming at. Research would've provided a uniform basis for everyone who is willing to participate in a discussion about the same thing and assuming the same conditions. I think the recommendation for down voting when no research effort is shown applies here perfectly. Nothing against the OP, I've also seen it often enough that not so good questions turned into great ones after a bit of tweaking $\endgroup$ – Raditz_35 Jun 20 '18 at 10:02
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From your question you seem assuming that atmospheric density has an effect on punching/kicking.

The only reasons why this would be possible are:

  • changed air resistance because of the different air density
  • changed metabolism due to the different air amount

We can safely exclude the first effect. Air drag becomes significant above 30 km/h, or about 8 m/s. Punch velocities are estimated to be lower than that, around 1 m/s to 7 m/s. Also, the time it takes for a punch to hit is so short that any practical influence of the above effect would be negligible, as opposed for example with what would be on riding a bike trying to break the hour record.

About the second point, it is known that different air density affects muscular performance, due to the different intake of oxygen with breathing.

However the organism slowly adapt to the different conditions, with the process called acclimation

is the process in which an individual organism adjusts to a change in its environment (such as a change in altitude, temperature, humidity, photoperiod, or pH), allowing it to maintain performance across a range of environmental conditions. Acclimatization occurs in a short period of time (hours to weeks), and within the organism's lifetime.

The text above seems suggesting that the performances are kept unchanged after acclimation, therefore I would expect no particular changes in the hitting yield.

Again, a single punch is not so demanding that any significant effect can be perceived even during acclimation (if I was to be hit by Mohamed Ali immediately after his landing in Kinshasa I would have been knocked out anyway). Different is the story if you extend the effort.

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    $\begingroup$ +1 L.Dutch, as an addition for you, the effectiveness of a punch/kick/shove, is down to force applied (Mass x Acceleration) would the mass of the puncher be higher or lower if the air density changed, no. weight slightly but only a negligible amount, and so would the weight of the punched, so it cancels out, would the acceleration change, by only the most fractional percentile due to drag, but as L.Dutch says not enough to be noticeable, therefore force is the same so the effect is the same $\endgroup$ – Blade Wraith Jun 20 '18 at 10:19
  • $\begingroup$ There wold also be a very slight increase in the initial resistance of the body being struck to its induced differential movement in the opposite direction (caused by the transfer of momentum via impact force) which means that during that slightly increased lag, the struck body would be very slightly more compressed in the vector of the strike. $\endgroup$ – GerardFalla Jun 20 '18 at 16:25
  • $\begingroup$ In older martial art movies we can hear a rather loud whooshes of air as combatants try to throw kicks and punches. $\endgroup$ – Alexander Jun 20 '18 at 16:28
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    $\begingroup$ @Alexander yes, we can. It is a trick to make them appear faster than they really are to viewers. $\endgroup$ – Mołot Jun 20 '18 at 17:40

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