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38

You feel cold when heat is flowing from you to the surroundings, your body tries to burn more energy to keep up your temperature, so you shiver. Water conducts heat much more effectively than air (more than 100x as well) so even with water at the same temperature as air you will lose a lot more heat and feel cold. When your body is too hot it losses energy ...


13

Different parts of the eye have different response speed. The corner of your eye doesn't see color, but is fast; the center sees color, and is slower. This means that when you look at a 60 Hz monitor straight-on, the image is perfectly steady; but when you look at it from the corner of your eye, it is flickering. As you go to even higher frequencies of ...


7

Short answer: mostly no. Slightly longer answer: the interaction of neutrinos with the molecules of your body take several forms, but they all come down to ionizing dose. However, there are many larger sources of ionizing dose in your like. Things like the Potasium-40 in the food you eat, radon and Carbon-14 in the air you breath, cosmic rays, and on and ...


4

When you feel hot, you perspire so as to benefit by evaporative cooling. As the relative humidity gets closer to 100%, the sweat cannot evaporate and evaporative cooling becomes less effective. Liquid water is a much better conductor of heat than air (even humid air) is, so if the water is even a few degrees cooler than your body, you feel cold because the ...


4

1&2) Let's suppose there are only two forces in play: the one exerted by the man, and weight. The sum of works done on the body equals the variation of kinetic energy (this is a theorem of mechanics; I fail to find its English name). Since the body has no velocity at the start and at the end, the sum of works is zero. The net work done by the man on ...


3

No animal, object or person defies gravity. Not here on earth, not in any place on the universe. Ask yourself this question on another form: When a plane, or a bird, flies, is he(it) defying gravity? No! They are just balancing forces, pushing air behind then, so it can compensate their weight. The direction of the resultant vector of forces combined, is up. ...


2

As yet unknown - there are some hints that life might exist ie methane emissions, but no proof.


2

If you ignore air resistance, and assume the surface is hard and absorbs no energy that you need to care about, then the remaining energy must be absorbed as heat in your body (and shoes). If your temperature is steady then you will lose energy through heat radiation and convection at the rate you use it. There will be many different chemical and mechanical ...


2

You can calculate the air drag along your arms using the formula for air drag, $F = \frac{1}{2} \rho u^2 c_D A$, takin $u$ the speed at which they'll effectively move relative to air, and $A$ their projected area on the plane perpendicular to motion. $\rho$ is the density of air, that's why it's so much less efficient than in water. $c_D$ will be close to ...


2

1) What can be say about the work done by the man to the weight? Unlike gravity, the force exerted by the man is in general not constant, does not depend only on position of the body (you may apply different force on the weight at the same height $h$ on the way up vs. on the way down), and is not conservative (does not arise from a potential). When the ...


1

There's an important difference between liquid water and water vapor. The difference is 539 calories per gram to be exact. That's why being in humid air makes you hotter - the water vapor has all this latent heat it can release upon you by condensing. Equivalently, it prevents your sweat from evaporating and absorbing this energy. Liquid water doesn't have ...


1

You are describing two different mechanisms of cooling the human body: 1) When we sweat our body produces fluids that tranfer heat from us through their evaporation (fluids gets the heat from our body and evaporate). One can easily understand that the more the surrounding enviroment has a highly humidity value , the more this heat- transfer gets ...


1

The correct statement is - the total work done on the weight is zero i.e. the total energy of the weight before and after the experiment is same. However, when the man is lifting the weight he is obviously working against gravity. More importantly, when he is lowering the weight, he is still working against gravity, as gravity would rather lower the weight ...


1

It has been found that gravity, understood as force, acts on any body of any shape or material depending only on the mass of the body. In fact, gravity understood as the curvature of spacetime acts on all of matter and energy, including light. In this way, nothing defies gravity: it is one of the most universal phenomena known to man. Colloquially, one ...


1

The conscious part of the human brain cannot process visual information that persists for less than about .04 seconds while the subconscious part is thought to be faster. What the brain is doing is pattern recognition in either case (which requires a considerable amount of mental processing). The issue is how long does this mental processing require and the ...


1

What is the potential energy of the human body? 36 MJ $\simeq$ 8600 kcal. The basal metabolic state for a human is about 60 W. Let's assume (horrible) an immobile person dies after one week (604800 s) of starvation, he will have consumed 60 W * 604800 s = 36,288,000 J. Where does this energy come from? from the high energy chemical bonds of ...


1

The definition of entropy can be found on Wikipedia. It's the integral of the reversible heat flow divided by the temperature at which the flow occurs. This has, at face value, nothing to do with order and disorder because there is no obvious way to even define structure in thermodynamics. One has to understand the link between thermodynamics and ...


1

The heart only acts as a big dipole, when it is electrically active. ECG measures the potential difference between different places on the skin. These potential differences are created when different parts of the heart muscle are in dfferent stages of their action potential. For example, when the septum and the subendocardial myocytes are depolarized, but ...


1

One way the body uses to lose temperature is by sweating. If the humidity of the environment is high, the the sweat can't vaporize(the environment won't accept it) and thus the water on the body gets warmer and we feel even more awful. But there are other mechanism by which the body loses energy and thus temperature. One of the main mechanism is via ...



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