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

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SUMMARY

The discussion centers on the physics of weight and force, specifically addressing the misconception that one can increase their weight without changing mass. Participants clarify that while a person cannot add weight, they can exert additional downward force through muscle engagement, making it harder to lift them. The conversation highlights the difference between living and non-living entities in terms of force exertion, emphasizing that living beings can apply internal energy to enhance their downward force. The experiment discussed illustrates the principles of force and resistance in a practical context.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Basic knowledge of force and weight concepts
  • Familiarity with muscle engagement and its effects on lifting
  • Awareness of the difference between mass and weight
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  • Research Newton's Second Law of Motion and its implications on force
  • Explore the concept of muscle engagement and its role in physical exertion
  • Investigate experiments demonstrating the relationship between force and weight
  • Learn about the biomechanics of lifting and resistance in living organisms
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This discussion is beneficial for physics students, fitness enthusiasts, and anyone interested in understanding the dynamics of force and weight in practical scenarios.

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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