All Questions
Tagged with everyday-life biophysics
10
questions
182
votes
14
answers
77k
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Why does holding something up cost energy while no work is being done?
I read the definition of work as
$$W ~=~ \vec{F} \cdot \vec{d}$$
$$\text{ Work = (Force) $\cdot$ (Distance)}.$$
If a book is there on the table, no work is done as no distance is covered. If I ...
- 5,377
29
votes
10
answers
10k
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What's the difference between running up a hill and running up an inclined treadmill?
Clearly there will be differences like air resistance; I'm not interested in that. It seems like you're working against gravity when you're actually running in a way that you're not if you're on a ...
aaron
2
votes
3
answers
6k
views
Why the pressure of atmosphere doesn't crush you when you e.g. walk outside?
Why the pressure of atmosphere doesn't crush you when you e.g. walk outside? I mean the density of air is $1.26 kg/m^3$, so with $100 km$ above us, it exerts much pressure on you when you walk outside....
- 735
-4
votes
3
answers
3k
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Life and Death, and Energy Conservation
Humans are born and they die. When we are born, is energy created? Or is it just some amount of energy that our mother gives us? Doesnt she take this energy from the surroundings? If so, then when we ...
- 1,128
18
votes
3
answers
10k
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Which requires more energy: walking 1 km or cycling 1 km at the same speed? [closed]
I feel more tired walking 1 km than cycling 1 km at the same speed. However when cycling I am moving the extra weight of the cycle along!
- 933
23
votes
4
answers
108k
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How much energy in form of heat does a human body emit?
How much energy in form of heat does a human body emit at rest level?
- 343
8
votes
11
answers
1k
views
Is it more work to put more (apparent) effort to get the same outcome?
I was taking my dogs for a walk yesterday evening when this question occurred to me.
The two dogs were pretty enthusiastic about the walk and wanted to run on ahead, so the leads were taut and they ...
- 257
2
votes
2
answers
977
views
Order of magnitude estimation for some intriguing questions
The physics TA showed us a few examples in which one can estimate many things from first principles, sound logic, and scaling arguments. This led usually to understanding of why some numbers have the ...
- 17.1k
1
vote
2
answers
474
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What's Optimal About Six Legs According to Physical Laws? [closed]
In many respects the insects can be regarded as the most successful class of animals in evolutionary terms. And one of the most common features of insects is that they (mostly) all have six legs.
Not ...
- 11.7k
0
votes
3
answers
315
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Work power and energy
When you push your bicycle up on an inclined the potential energy of the bicycle and yourself increases. Where does this energy come from?
user60881