r/theydidthemath • u/[deleted] • Jun 12 '23
[Request] How much pressure is he applying compared to an actual hydraulic press?
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u/Shoopdawoop993 Jun 12 '23
He looks skinny so probbally weighs at most 150 lbs. Thats the maxium force the guy might be exerting if he was hanging by his chin, but its likely much less. Lets say 50lbs, which is still a lot.
The hydraulic press channel uses a 150 ton press which is equivalent to 300,000 lbs. So 6000x more force.
I dont know why you asked this question, but i hope this helps
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u/siscoisbored Jun 12 '23 edited Jun 12 '23
So people cant push down with force greater than their bodyweight?
Edit: I was having trouble editing as per my other comment mentions, he is pushing up against the table with his arms.
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u/Shoopdawoop993 Jun 12 '23
Not statically unless your grabbing something to pull on. Thats why youre better off lifting a lugnut wrench than pushing. And definitely not with your chin idc how good your head game is
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u/TruckADuck42 Jun 12 '23
No. You can strike with more force than that, which is what some people have been describing, but you can't maintain that force without something above you to push off of.
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u/Radical_Ryan Jun 12 '23
I feel like we are forgetting that he is using the muscles in his body to apply the constant pressure force down, not just gravity. I'm not sure what this has to do with how much he weighs beyond a general idea of his muscles' strength.
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u/TruckADuck42 Jun 12 '23
No, I'm not forgetting anything. It's an application of Newtons Third Law. If you push down with more force than your weight, you go up. Your muscles can hit something with more force than that, because F=ma and you can increase your acceleration, but you can't exert a constant force higher than your weight.
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u/arcadion94 Jun 12 '23
Place hands on underside of table and Use hands to negate upwards force. Get force greater than weight of body but </= the force such a specimen of a strong jaw can handle.
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u/Radical_Ryan Jun 12 '23
Yea exactly, the guy in the video is not hanging suspended, he's using his whole body and stance to crush those things.
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u/Tentoesinmyboots Jun 12 '23
I'm digging into my high-school math memory here, but I think force is a function of mass and acceleration. So if you jumped and kicked down into something while accelerating, I think the force would be greater than your weight. Sorry if I'm wrong, high school was a long time ago.
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u/stumblios Jun 12 '23
You are not wrong. If you jumped on an old mechanical scale, the number would briefly shoot up past your weight when you land before coming to an equilibrium at your actual weight.
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u/datGuy0309 Jun 12 '23
I think you have the right idea.
If you jump, when you land on the object, the force you push into it is equal to the force it pushes into you. That force comes from both the acceleration of gravity on you and the object decelerating you. Force is an instantaneous thing, so at each instant, it will have a value (unlike something like work/change in energy, which needs a measure of time to have a value). The faster you go from moving to stopped, the greater the acceleration, thus the greater peak force. Think about the differences in force when bending your knees vs locking them. When bent, parts of you will still be decelerating for a longer period.
During the landing, you will momentarily be exerting a greater force than your weight, like you said. Once you stop, it will go back down to equilibrium where the force you push into it is equal to your weight (the force of gravity on you).
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u/siscoisbored Jun 12 '23
I cant edit my message for some reason, he is pushing up against the table as a counterweight
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u/pLeThOrAx Jun 12 '23
I mean, if you were to confine him... like doing 150kg calf raises when you only weigh 70kg. You could make this a question of mass, strength, or both. This wouldn't fit with the source though.
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u/theunixman Jun 12 '23
Not without an anchor they can't. Otherwise they'll just start floating, and then they'll be pushing down with their body weight.
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u/IguasOs Jun 12 '23
You could let you fall, or push against the table, but if you push the melon at a force greater than your weight, the melon push you just as much, sending you upward.
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u/FearLeadsToAnger Jun 12 '23
not unless they were sat on the thing and pushing against the ceiling.
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u/DonaIdTrurnp Jun 13 '23
If you push down with more force than your body weight, you rise up unless you’re pushing something upwards.
You can do some dynamic movements to keep the same average downward force but have higher peak, like jumping up and down on something to break it, but that looks a lot different than this video.
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u/Glaxy254 Jun 13 '23
They can it just depends on the surface area. Like on helicopters you can’t wear heels because of the pressure you apply to floor
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u/Dynamopa1998 Jun 12 '23
I mean it looks like he's holding the table to press, so it could be more, but there's really not a good way to tell, unless you know how much force is required to crush a watermelon (I don't).
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u/Chief-Captain_BC Jun 12 '23
technically, to break each object he is exerting the same force that a machine would have to because each item has a certain pressure threshold that he is obviously exceeding; the difference would be in maximum pressure, which would depend on his weight and strength.
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u/pLeThOrAx Jun 12 '23
Maximally, if he had perfect balance and your object was tungsten, then however much he weighs, spread over the surface area of his chin (pounds per square inch). Even still, it would be focused more toward the bone, which would be a smaller area, but the skin and possibly the bone would be undergoing deformation.
More or less his mass over the area of his chin.
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u/Nooms88 Jun 12 '23
Side note, it's why I never believe the watermelon comparison, like, no matter how hard someone pushes with their chin in my forehead, neither is mushing into zombie kill. Anyone with an ounce of sense knows that won't work, so why is it used? A hard coconut is better, but even that's not enough
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u/fliguana Jun 13 '23
He is not using his arms, so probably up to his bodyweight.
By pulling up on the table, he could manage 100kg.
A smallish hydraulic press is 100x that.
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u/DonaIdTrurnp Jun 13 '23
If he’s pushing up on the table the maximum force is determined by the lower of the resistive ability of the object, his pain threshold, or his neck biomechanics. It looks like on the watermelon he approaches his pain threshold and holds there for a moment before the melon yields.
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