I've seen people argue that lighter people can take a punch better because they can "go with it" better.

This seems plausible to me, but is it really true?

One reason why it seems plausible is that indeed, if you are heavier, you will move back slower as a result of the punch, which means that the fist is also moving slower as you are going back; this means that more of the kinetic energy of the first was absorbed by your body.

  • $\begingroup$ Athletes (boxers etc.) who take punches well don't do it acting as passive targets; they use techniques such as rolling and slipping to avoid taking the full force of the punch. And if the target is very heavy, i.e., the ratio $M_{target}/M_{puncher} \rightarrow \infty$ the target is not going to be affected much, right? $\endgroup$ – Maxim Umansky Apr 24 at 6:08

Well, theoretically, purely by means of simplified mechanics, lighter people can take it better.

As even for partially inelastic collisions like punching, the law of momentum conservation is honoured.

In such collisions, lighter objects have higher ratio of kinetic energy versus momentum.

E.g. guns are known for recoiling during shooting. But if the gun had 100 times higher mass than a bullet then (neglecting the gases ), the bullet has 100 times higher kinetic energy then the gun.

But finally, even if the lighter body may have less energy to absorb inelastically, it may be overruled by lower endurance, so less energy may cause bigger damage.


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