Energy spent on holding a kg

  • Thread starter jc.int
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  • #1
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Main Question or Discussion Point

hello,
If I hold 1kilogram at one meter of the groud during an hour, what would be the theoretical energy I am spending (in joules for example)?

Thank you,
Jaimie
 

Answers and Replies

  • #2
cepheid
Staff Emeritus
Science Advisor
Gold Member
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You're not doing any work because the displacement of the object is 0.

However, your muscles, as a biological system, are inefficient. To just bear a load without moving it, they must alternately contract and relax rapidly. As a result, your body expends chemical energy and you do end up feeling tired.
 
  • #3
610
5
You're not doing any work because the displacement of the object is 0.

However, your muscles, as a biological system, are inefficient. To just bear a load without moving it, they must alternately contract and relax rapidly. As a result, your body expends chemical energy and you do end up feeling tired.
Indeed. And as a result, the amount of energy expended depends more on your muscle tone, circulation, metabolism, etc. then on simple physics of the weight and gravity. Place the same kilogram on a solid table for an hour and it becomes obvious that no energy is being expended (the table does not run down its batteries/use up its fuel, etc.)
 
  • #4
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I agree with you but when a helicopter holds a weight it is using energy to compense the gravity force, isn't it?
 
  • #5
cjl
Science Advisor
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383
Yes, because once again, it is inefficient. A helium balloon can hold a weight as well, and it would require no energy input to do so.
 

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