Question about weight/mass/force I can´t explain

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  • Thread starter Thread starter Cvitanic
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Discussion Overview

The discussion revolves around the concepts of weight, mass, and force, particularly in the context of a personal experiment involving lifting a person who attempts to exert additional downward force. Participants explore the implications of this scenario and the mechanics involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes an experiment where they lifted another person who attempted to "make herself heavier" by applying downward force, leading to difficulty in lifting.
  • Another participant asserts that one cannot increase weight without changing mass, humorously suggesting chocolate as a means to increase mass.
  • A participant questions the setup of the experiment and suggests using scales to measure weight while pushing down, indicating that without a fixed object to push against, the weight reading should remain unchanged.
  • It is proposed that the difficulty in lifting may be due to the person exerting horizontal pressure, which could complicate the lifting effort.
  • One participant introduces the idea that living beings can exert additional force beyond their weight due to internal energy from nutrition, contrasting this with non-living objects.

Areas of Agreement / Disagreement

Participants generally agree that one cannot simply increase weight without changing mass, but there is disagreement regarding the mechanics of exerting additional force and the implications of the experiment. Multiple competing views remain on how force is applied and perceived in this context.

Contextual Notes

Some assumptions about the nature of force exertion and the mechanics of lifting are not fully explored, and the discussion includes various interpretations of the experiment's outcomes.

Cvitanic
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Hi everyone ! I´m posting as I couldn´t find any information on the forum, or maybe I can´t find a way of searching.

My question is based on a discussion me and my girlfriend had about "making yourself heavier", and we tried a little experiment: First I lifted her in my arms without any problems, and then I tried a second time while she "applied downwards force" or "tried to make herself heavier" and obviously was harder to lift. She claimed that the second time she tried to "anchor" down, but I insisted that was impossible since she could not add "weight" or increase the downwards force without acceleration.

It´s kind of complicated to explain, but I´ll try to draw something to make more sense ! If anyone quite understood my point, all interpretations will be welcome ! Thanks !
 
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She can't make her heavier without changing her mass (chocolate works for this)
There are a couple of 'magic tricks' where you lift someone - then press you arms downward - then fail to lift them. It's all to do with muscle memory etc.
 
Good Point there with the chocolate !

I totally agree, you can´t make yourself just "heavier" but then the question remains... It was obvious it was way harder to lift her when she tried to "push down" and it wasn´t fatigue, cause we tried the "heavier" setup first, and the second time she "lightened up" and it was much easier then...
So ?
 
What exactly was the setup ?

A simple test is have the person stand on a pair of scales and 'push-down' assuming they can't push against some other fixed object (like the ceiling) they can't change the steady reading on the scales
 
Welcome to PF!

mgb_phys said:
… (chocolate works for this)

Flowers work also! :biggrin:
Cvitanic said:
… and then I tried a second time while she "applied downwards force" or "tried to make herself heavier" and obviously was harder to lift. She claimed that the second time she tried to "anchor" down, but I insisted that was impossible since she could not add "weight" or increase the downwards force without acceleration. …

Hi Cvitanic! Welcome to PF! :smile:

If she "tried to make herself heavier" by "anchoring down", and if you were holding her with both your arms, she was probably exerting a horizontal pressure pushing them apart, which would make harder work for you.

Try again using just one hand! :wink:
 


tiny-tim said:
Flowers work also! :biggrin:


Hi Cvitanic! Welcome to PF! :smile:

If she "tried to make herself heavier" by "anchoring down", and if you were holding her with both your arms, she was probably exerting a horizontal pressure pushing them apart, which would make harder work for you.

Try again using just one hand! :wink:

Sounds about right... I´ll try your idea !
 
this is difference between the living and non living things, non living things can exert force of only of ther weight but living things can add the force beside their weight by using internal energy because we eat food and have nutrition,
this is the reason for what i have understood , were u asking same things ?, let me know
 

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