The use of methods from the physical sciences to aid in the study of biological systems. Note that biophysics questions are only allowed if they are mainly about physics.
Questions tagged [biophysics]
696 questions
188
votes
14 answers
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 hold up a book in my hand and my arm is stretched,…
SMUsamaShah
- 5,507
88
votes
3 answers
Why can Hiroshima be inhabited when Chernobyl cannot?
There was an atomic bomb dropped in Hiroshima, but today there are residents in Hiroshima. However, in Chernobyl, where there was a nuclear reactor meltdown, there are no residents living today (or very few). What made the difference?
user14154
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84
votes
3 answers
Why is the sky not purple?
I realise the question of why this sky is blue is considered reasonably often here, one way or another. You can take that knowledge as given. What I'm wondering is, given that the spectrum of Rayleigh scattering goes like $\omega^4$, why is the…
Warrick
- 9,870
79
votes
8 answers
Does quantum mechanics play a role in the brain?
I'm interested in whether the scale of processes that occur in the brain is small enough to be affected by quantum mechanics. For instance, we ignore quantum mechanics when we analyze a game of tennis because a tennis ball is much too large to be…
QCD_IS_GOOD
- 7,145
72
votes
3 answers
How can ants carry items much heavier than themselves?
This morning I saw an ant and suddenly a question came to my mind: how do ants actually carry items much heavier than themselves?
What's the difference (in physics) between us and them?
Paul
- 3,475
67
votes
15 answers
Why is ascending some stairs more exhausting than descending?
I have been asked this question by school kids, colleagues and family (usually less formally):
When ascending a flight of stairs, you exchange mechanical work to attain potential Energy ($W_\text{ascend} = E_\text{pot} = m gh$).
However, when…
Daniel
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58
votes
7 answers
Cyclist's electrical tingling under power lines
It's been happening to me for years. I finally decided to ask users who are better with "practical physics" when I was told that my experience – that I am going to describe momentarily – prove that I am a diviner, a psychic, a "sensibil" as we call…
Luboš Motl
- 182,599
55
votes
8 answers
Short of collision, can gravity itself kill you?
Imagine that you are falling into object with huge gravity (i.e. black hole) that does not have any atmosphere.
The question is - before you hit the ground, can the gravity itself (which would be extremely huge) kill you? And if so, how exactly that…
libik
- 661
45
votes
12 answers
Does physics explain why the laws and behaviors observed in biology are as they are?
Does physics explain why the laws and behaviors observed in biology are as they are? I feel like biology and physics are completely separate and although physics determine what's possible in biology, we have no idea how physics determine every…
user236241
40
votes
4 answers
Why is the efficiency of human cells less than the efficiency of an Otto engine?
I always used to think (I don’t know why!) that the efficiency of human (and animal and plant) cells should be equal to or near the efficiency of a Carnot engine or at least should be the highest efficiency among all practical engines. But I…
lucas
- 3,199
35
votes
4 answers
Why does light of high frequency appear violet?
When people are asked to match monchromatic violet light with an additive mix of basic colours, they (paradoxically) mix in red. In fact, the CIE 1931 color space chromaticity diagram shows this effect begins at about 510nm (greenish-cyan), where…
wnrph
- 1,297
35
votes
4 answers
The physical definition of work seems paradoxical
So this is possibly a misunderstanding of the meaning of work, but all the Physics texts, sites, and wiki that I've read don't clear this up for me:
In the simplest case with the simplest statement, work is force times distance. If you push with a…
Addem
- 1,249
33
votes
11 answers
Why does running spend more energy than walking?
The study energy expenditure of walking and running concludes that running spends more energy than walking.
My understanding is that although running makes one feel more tired, that only indicates that the power was higher (since the time of…
LoremIpsum
- 534
33
votes
5 answers
If two sound waves that are different frequencies create beats that occur several hundred times per second, can you hear this effect as its own tone?
If you have multiple waves of different frequencies, the interference from the different waves cause "beats".
(Animation from https://en.wikipedia.org/wiki/Group_velocity)
Let's say that a green dot in the above animation reaches your ear a few…
Daniel M.
- 445
33
votes
3 answers
Is plant photosynthesis more efficient than solar panels?
Is photosynthesis more efficient than solar panels? If so, by how much?
Chris Laforet
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