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4
votes
2answers
745 views

Is any work done when I walk?

I am trying to figure out the amount of work done when I walk X miles or for X minutes. So I got Work=Force x Distance and Force=Mass x Acceleration and Acceleration=(change in velocity)/time. I am ...
13
votes
3answers
5k views

Google interview riddle and scaling arguments

I am puzzled by a riddle to which I have been told the answer and I have loads of difficulties to believe in the result. The riddle goes as follows: "imagine you are shrunk to the size of a coin ...
2
votes
2answers
106 views

Harmlessness of a pure alpha decay particle

From my high school physics class I remember that there are some particles which exhibit pure alpha decay (i.e. alpha decay to there stable isotope), like Po-210, Po-211 and Bi-209. What I also know ...
-1
votes
1answer
185 views

Temperature gradient in body [closed]

Is there a Temperature gradient in the human body? especially I have heard that the eye is colder than other places? Is that right?
43
votes
3answers
24k views

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 ...
4
votes
1answer
159 views

What is the minimum pressure difference for your ears to pop?

I'm assuming the answer to this largely varies from person to person. Assuming you could instantly change the pressure around your head by amount $\Delta p$, what is the minimum $\Delta p$ for your ...
16
votes
2answers
982 views

Why can't Humans run any faster?

If you wanted to at least semi-realistically model the key components of Human running, what are the factors that determine the top running speed of an individual? The primary things to consider would ...
0
votes
1answer
102 views

Atoms in our body

Our body of course exchanges some atoms with environment every day however are there some of atoms which stay with us a life time?
10
votes
2answers
13k views

Effects of a very large magnetic field on the human body

Ever since reading about the NHMFL I have always wondered about this and asked several people without getting a good satisfactory answer. My question is, considering the simplest case let's say a ...
4
votes
2answers
203 views

Do viruses suffer from quantum de-localization?

Consider some microscopic life form. It should obviously be localized in space, in the quantum-mechanical sense, if it is treated as a single particle (though it is composite). If its characteristic ...
1
vote
0answers
74 views

Concentration of Proteins

You release a billion protein molecules at position $x = 0$ in the middle of a narrow capillary test tube. The molecules’ diffusion constant is $10^{−6} \ cm^2 s^{−1}$. An electric field pulls ...
4
votes
1answer
152 views

Radiation exposure to a child who was briefly in the presence of an adult who had received a 18FDG PET scan

I am a physician who thought she was good at math, but apparently am not as I cannot figure out this mathematical/physics question. (My background is obviously NOT nuclear medicine!) A family friend ...
0
votes
1answer
33 views

Measuring life through radiation

Dramatic title, I know. But it's shorter than Measuring a person's effective mass through radiation and comparing it to their weighed mass and I figured this would get people's attention. I just ...
1
vote
2answers
167 views

Was the early Earth radioactive?

I've been reading of the (surprising) fact we are uncertain on whether there is nuclear fission in the center of the Earth or not (yet we know so much detail on structures at the other end of the ...
2
votes
2answers
193 views

Computing microstate probabilities based on Boltzmann distribution for chemical systems - Is it rigorous?

One approach to predicting the folded structure of a polymer (DNA, RNA, protein) is to compute the probability that any particular part of the polymer $x_i$ is "paired" with another part of the ...
4
votes
2answers
7k views

How efficient is the human body?

This question sort of comes to mind when hearing how efficient an internal combustion engine is turning chemical energy in mechanical energy (something like 20-40%) with lots of excess heat. As an ...
0
votes
2answers
1k views

How neutrinos can be harmful?

What are the circumstances in which neutrinos can harm humans or even kill them.?
13
votes
5answers
841 views

Octave equivalence: biological or more?

I'm a graduate student in mathematics doing a bit of research in signal processing and Fourier analysis and I've come across a question that could probably be better answered by a physicist: Is the ...
1
vote
4answers
15k views

Earth's Magnetic Field, Human Brain and Sleep [closed]

I remember reading somewhere: when you sleep in a way subjecting your body to cut the geomagnetic field at right angles, you become highly emotional whereas when it is Parallel, it cools your ...
17
votes
3answers
813 views

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 ...
0
votes
1answer
413 views

What is the difference between “in-plane shear modulus” and “shear modulus”

In the wiki it is article only about shear modulus and it is written that it's unit is Pascal. At the same time in all researches about Red Blood Cells shear stresses, authors write "in-plane shear ...
0
votes
1answer
475 views

How is tritium illumination possible without negative health effects?

Turns out there's tritium illumination - a tiny very strong plastic tube will be covered in phosphor and filled with tritium. Tritium will undergo beta decay and a flow of electrons will cause the ...
0
votes
2answers
162 views

How much time can I power my laptop by eating one dessert?

Random question that popped into my mind after a 4-hours power outage. Let us assume that I am eating an extra dessert (250 kcal) and that I am using a bike and a generator to power my laptop (it ...
0
votes
0answers
81 views

Visualise the sound intensity

I'm studying Biophysics and my current subject is sound. One of the properties of sound is intensity. From my notes I can see the following definition: Intensity Formula is: $(I = w*m^{-2})$ or $(I = ...
1
vote
1answer
700 views

What is physics of a normal jump?

What is the physics behind a normal human jump ? when a normal human wants to jump. First, some energy is stored in their thighs and The elastic tendons Just like a spring. In mechanics and ...
3
votes
1answer
155 views

Why do beverages taste different based on how cold they are? [closed]

Why does temperature effect the taste of beverages? Specifically, how does the temperature for example mask certain tastes ie filtered vs unfiltered water taste very similar at colder temp and Is ...
2
votes
1answer
415 views

Is it dangerous if one elementary particle with high energy penetrates our brain?

We might be killed if a bullet penetrates our brain. How about an elementary particle moving with high energy penetrates our brain? Assume that we can have exactly a single elementary particle for ...
2
votes
2answers
193 views

Can wireless power transfer harm organic life by anyway?

Now, humanity can beam 50-60 watts power through 10 centimeter-thick concrete block. Can such wireless power transfer harm us by anyways?
2
votes
2answers
172 views

Is metabolic rate the amount of heat given off?

The Basal Metabolic Rate is intuitively expressed as "the amount of energy you consume just sitting around." In some places it seems to be equated with the amount of heat that you give off. Is this ...
0
votes
1answer
163 views

Dynamic Light Scattering

In the Dynamic Light Scattering experiment, how is the intensity distribution plotted against time, keeping in view the multiple scattering of photon particles in laser ?
43
votes
7answers
4k views

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 ...
2
votes
1answer
198 views

Examples of piecewise smooth dynamical systems [closed]

I have recently been studying continuous dynamical systems whose phase space can be divided into a number of regions. Inside each of these the flow is smooth, but there is a discrete jump in the flow ...
31
votes
3answers
4k views

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 ...
4
votes
2answers
313 views

Why don't massive water-borne animals crush under their own weight when they're in water?

If you take a giant whale out of the water and put it on land for long enough, it will crush itself under its own weight. Why doesn't the animal get crushed under its own weight when it's in water?
4
votes
2answers
478 views

Human perception of distance

When we see things around us, distant objects look smaller to our eyes than nearby objects do. Is there any physics-related reason why our eyes or brain perceive things like this? Or if this is ...
0
votes
2answers
1k 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 ...
1
vote
0answers
42 views

Is energy applied by the muscle when it holds a body in the air? [duplicate]

Possible Duplicate: Why does holding something up cost energy while no work is being done? We all know the following Newtonian formulas: PotentialGravitationEnergy=m*g*h Kinetic Energy = ...
5
votes
2answers
3k views

How can an an ant lift 50 times its own weight and pull 30 times its weight?

According to many sites like this one, an ant can apparently lift 50 times its own weight and pull 30 times its weight. Is it true? Can it be proved using physics? Though most sites agree that an ...
2
votes
2answers
135 views

How Safe Are Heat Ray Guns?

Could a little meddling with the frequencies of the Heat Ray Gun beam result in frying crowds rather than dispersing them?
3
votes
1answer
984 views

How does a stronger magnet affect the MRI image quality?

In which ways is a stronger magnet better for magnetic resonance imaging? I read that: The field strength of the magnet will influence the quality of the MR image regarding chemical shift ...
13
votes
4answers
3k views

What does Peter Parkers formula represent?

Okay, so the trailer for the new Spider Man movie is out and appearently our friendly physicist from the neightborhood came up with something. However I can't find out what this is. ...
1
vote
2answers
1k views

How thin a filter to filter particles out of salt water to make salt for human consumption?

I have gathered some salt in the Death Valley and for the fun of it I would like to clean it and make it edible. The process I plan to follow is simple: Dissolve the salt in water. Boil water for ...
17
votes
2answers
3k views

How does space affect the human body (no space suit, no space craft)

How does "outer space" affect the human body? Some movies show it as the body exploding, imploding or even freezing solid. I know space is essentially a vacuum with 0 pressure and the dispersion of ...
0
votes
3answers
863 views

What are brain waves? [closed]

I watched a documentary showing that humans could alter the results of an experiment by thinking about it, and the data these people collected supported their hypothesis. And the reason these people ...
1
vote
2answers
343 views

What happens to body chemistry at the speed of light? [duplicate]

Assume that I'm traveling at the speed of light in one direction. My brain is also traveling at the speed of light in that direction. Presumably there is at least one receptor site in my brain that is ...
3
votes
4answers
3k views

Is it only red, green and blue that can make up any color through additive mixture?

I'm reading about color vision and have some trouble understanding the motivation for why the trichromatic theory was suggested in the first place. The book I'm reading ("Psychgology: The science of ...
1
vote
2answers
888 views

How does length of the bar affect force on the muscles?

Fitness Model, Rob Riches, claims that doing bicep curls with Olympic bars is different than lifting with normal bars. Biceps have always been a favorite muscle group of mine to train, but ...
7
votes
1answer
216 views

How can tunneling be one-way?

I was recently at a lecture given by Dr. Harry Gray, a biophysical chemist, where he talked about how proteins (specifically those involved in photosynthesis) are able to use various phenomena, like ...
4
votes
1answer
426 views

How do sunflowers rotate?

Is there a physics mechanism to explain how sunflowers rotate to always face the sun? I tried to find more information or references using google search, but no luck.
2
votes
1answer
2k views

How to calculate calorie expidenture from lifting a weight?

Am I correct to say that when a human lifts a dumbbell from, say, 2 feet off the ground to 6 feet off the ground, he will have increased the potential energy of the weight and thus will have burned ...