Person A and Person B are same person (theortically). They both weigh 800N. They both can vertically lift 1000N. They want to check something out.


Forces on Person A and Person B just standing

G -> Gravity; N -> "Normal"; M -> Muscular active
R -> Netto; 1 -> Person A; 2 -> Person B
$F_{g1} = 800N$
$F_{g2} = 800N$
$F_{m1} = 0N$
$F_{m2} = 0N$
$F_{n1} = F_{g1} - F_{m2} = 800N$
$F_{n2} = F_{g2} - F_{m1}= 800N$
$F_{r1} = F_{g1} - F_{n1} - F{m2} = 0N$ (no move)
$F_{r2} = F_{g2} - F_{n2} - F{m1} = 0N$ (no move)


  • Person A grabs Person B with both hands shirt of Person B in region of a bit lower than collarbone (like "tough" guys do on films).
  • Person A lifts Person B with 1000N in air, about 135 degrees relative to his torso.

When Person A lifts Person B

$F_{g1} = 800N$
$F_{g2} = 800N$
$F_{m1} = 800N$
$F_{m2} = 0N$
$F_{n1} = F_{g1} + F_{g2} = 1600N$
$F_{n2} = F_{g2} - F_{m1} = 0N$
$F_{r1} = F_{g1} - F_{n1} - F_{m2} = 0N$ (no move; on ground)
$F_{r2} = F_{g2} - F_{n2} - F_{m1} = 0N$ (no move; in air)


Seems till now, perfectly understandable and normal to me. In my perception of physics. This is when I lose it. Following rules, are total non-sense and also cause why I write this.

  • Person B grabs Person A with both hands whatever of Person A in region of whatever. By whatever I mean, somewhere on body that person is still able to pull Person A in air.
  • Person B lifts(?) Person A with 1000N in air(?), about 135 degrees relative to his torso.

$F_{g1} = 800N$
$F_{g2} = 800N$
$F_{m1} = 800N$
$F_{m2} = 800N$
$F_{n1} = F_{g1} - F_{m2} = 0N$
$F_{n2} = F_{g2} - F_{m1} = 0N$
$F_{r1} = F_{g1} - F_{n1} - F_{m2} = 0N$ ("floating")
$F_{r2} = F_{g2} - F_{n2} - F_{m1} = 0N$ ("floating")


"My brain", that gummy moisten tube in my head filled with baloney, tells me that first gravity and muscle force count. Then the normal one. This would cause $F_{r_{both}} = 0N$. They both have effect of being "freed" from effect of "normal" force. As Person 2 was when he/she was in air, being lifted by Person 1. But it's impossible. There is still gravity pulling them to earth. And at this point. There is "floating" going on and explaining this with "Normal force" would make it even worse because both of them separately will be either flying or falling through ground.

@edit - When Person A will pull Person B up. Person B's attitude would decrease till on feet. What then?

As if, if they normally stay on ground turning to tomatoes because of pulling each other up. What happens to that all the force they put in it? This 1600N.

"Definables": T-Shirt is untearable, won't fall off and does not hurt body at all. Both of them stay right on their feet. Please explain as plain as possible. I am really really really low with my knowledge. Relatively to you, I am idiot. I'm sorry for grammar.


Question: What happens to Person 1 and Person 2? Could you explain forces influencing their bodies, please?

Keep in mind I am teenager (17) without real physics knowledge. Answer may just lay around my point of view/knowledge/logic. In place of getting offensive try to explain where I made my mistake so it won't happen again :).

closed as unclear what you're asking by Olin Lathrop, BebopButUnsteady, Emilio Pisanty, Brandon Enright, WetSavannaAnimal aka Rod Vance Feb 25 '14 at 23:06

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • Please refresh. Got to correct grammar, spelling and what not. Changes don't change question or context. – user41325 Feb 25 '14 at 18:36
  • when B tries to pull A up newtons third law would not allow him to do that. i mean the opposing force would not allow B to lift up A while still in air. – Hubble07 Feb 25 '14 at 19:18
  • Huh? Too much handwaving. I lost track of who is doing what to whom. Also, just describe the problem, which probably wouldn't take more than 5 sentences. It doesn't sound like it should take any equations to explain the problem. – Olin Lathrop Feb 25 '14 at 19:24
  • @OlinLathrop If we would be as strong and weigh as much. I will lift you, and you will lift me. Well, my puny calculations prompts that both of them will fly. Why, how, when etc. . – user41325 Feb 25 '14 at 19:28
  • @Hubble07 "i mean the opposing force would not allow B to lift up A while still in air." what if they tried to lift each other, at once, in matter of reflex of 1 yoctosecond. – user41325 Feb 25 '14 at 19:31
up vote 2 down vote accepted

When the person in the air pulls upward on the person on the ground he is essentially applying an upward force on said person on the ground. This causes a downward force upon the person in the air. With no normal force to counteract this, the person in the air will just pull himself back to the ground.

  • And later? If they both are standing on ground? They both weigh 800N, but their muscular power is 1000N. There is still that 200N somewhere. – user41325 Feb 26 '14 at 13:18
  • So they actually make themselves "heavier"? edit - Thank you for not being like the others. – user41325 Feb 27 '14 at 18:30
  • No, sorry I believe my comment was unclear. Think about the forces on man a while they are both pulling upward on each other with equal force. There is the force of gravity going down, normal force going up, the force of man a pulling himself down, and the force of man b pulling man a up. As long as both men pull with the same force, these last two forces will equal out. The same is true for the forces on man b. Thus, the two men pulling on each other will exert no net force and both will remain on the ground. So the extra force is still there, but it results in a net force of zero. – wgrenard Feb 27 '14 at 19:26
  • Also, as further advice for asking questions, I believe the others closed your question because it was asked in an unclear manner. Honestly I didn't read through most of what you have up there; I didn't need to to get at what you were asking. I believe you would have had better results making your post more concise. – wgrenard Feb 27 '14 at 19:29
  • If you and one another understand this post. That means nothing is wrong with it. That's just laziness of people. You answered question in correct way. Thanks for answering and advice. – user41325 Feb 28 '14 at 16:06

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