New answers tagged

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What you are saying does make sense, and ties in with some of the points made in What makes running so much less energy-efficient than bicycling? Although you mention "putting a lot of energy into making the Earth flat", I do not think you are making an economic argument. You are merely asking if the superior efficiency of cycling is due to the fact that we ...


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For plastic water bottles of the market, Msha gave a video link ,in a deleted, unfortunately, answer because it just gave the link.For this case, plastic bottles, it should be the answer chosen. Crush the bottle fast, beginning from the bottom. The same will be true for any elastic type bottle. It is only glass bottles that have an unsqueezable limit. I ...


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The fastest way to get that liquid out of a bottle is to insert a lot of air in while the liquid comes out. How you insert a lot of air only depends on your imagination.


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I have two answers for this and one response to your strategies. 1 If the flow is infinity and you're trying to find pour rate averaged over infinite time. 2 response to what is mentioned. 3. Are strategies if the water flow is not infinite, hypothetical and is timed. 1.a It splatters or fluctuates in pouring because when water pours it builds a less ...


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go into a vacuum chamber open the bottle turn it upside down gravity will do it in a second or two.


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Hold the bottle upside down, your hand grasping it near the base. Extend your arm downwards. Make a circular, conical-shaped motion with your hand. Keep it up until you have a nice vortex going. Spinning too fast is counter productive; centrifugal force keeps too much water hugging the sides. You need a speed just a bit more than what's necessary to ...


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I assume you are not worried about the few drops that are always left in the bottle after pouring out the water. The reason I make this assumption is that without "evaporating lasers" being allowed every method suggested would need to wait hours for the drops to naturally evaporate. Even then, there would still technically be a tiny bit of water vapor in the ...


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Put an straw thru the open cap of the bottle. Bend the straw so that you can blow into it while it is upside down. Turn the bottle upside down and blow as hard as you can.


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It is unrelated to physics, but is part of a brand called psychophysics, that is, the study of perception. In the visual psychophysics branch of depth perception, you are interested in finding not only what depth information reaches your eye, but how and if all this information is used by your brain to estimate depth. Not all optic information is there to ...


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Hair, like fingernails and animal horn is made up mostly of a protein called Keratin. The strength and hardness of this polymer is caused by three types of chemical bonds: salt (ionic) bonds, hydrogen bonds and disulphide bonds. Water can significantly break the first two types (but not the disulphide ones). Significantly wetting hair thus leads to making ...


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I hear this regularly. I think its a combination of the effects above. The first effect is a front of compressed air being forced ahead of each of the trains. But then, as the fronts of the trains meet and pass, the Bernoulli effect leads to lower pressure between the trains. But this isn't uniform, each carriage has its own mini air front, and the carriages ...


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I am telling this from my practical experience. In my home we have very poor water supply so we purchase 15 ltr water dispenser for drinking water. The guy needs to take the bottle back. So he shakes the bottle such that water make a kind of whirlpool while still keeping it straight and then quickly turns it upside down at an angle. The water flows quickly ...


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You spin the bottle so that the water comes out like a tornado. This lets the air come in faster through a tube of space in the middle. The air pushes up forcing the water out leaving a space in the middle for air to come in. The rate of water flow is exponential. This is because the water lessens letting air come in faster, pushing the water out faster with ...


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My high school physics teacher was saying that “this is because of interference of sound waves. During the day, there are a lot of sounds and they cancel each other due to interference. But, during the night, there are few sounds and they can reach to our ears without canceling each other”. You need a better high school physics teacher. Temperatures tend ...


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If we suppose that the phenomenon you describe is related with wave interference. A wave is a kind of mechanical disturbance in the medium through which it is travelling. A sound wave consists of areas of relatively high and low energy, in the form of relatively high and low pressure. To understand how sound is produced, consider a speaker. The cone or ...


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I would tend to agree that background noise is a factor, but rather than reducing, adding to the sound you are trying to make sense of. So part of that may be how your brain is able to filter the information from the background noise. But at night the temperature is lower and according to this tutorial on sound propagation (which does cite reliable ...


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We must all keep in mind that for average atmospheric pressure, and assuming Zhang could pull a hard vacuum with his abdomen (which is probably not feasible, but serves to provide us with a bound), the maximum (negative) pressure he could achieve is only about 14.7 psia. Given 36 tonnes, you can back calculate what the diameter of the bowl would have to be. ...


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The exact mechanism you describe for how suction cups work is how the rice bowl work. Instead of the bowl being flexible, though, it's his body (skin and muscles) that are providing the change in volume necessary for the suction. So, instead of the suction cup creating the volume change, it's the surface the suction cup (the bowl) is attached to, Mr. Zhang'...


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Yes. It's is not so much the water is the beach sand reflecting light back to you like a parabolic mirror. The droplets of water on your skin can form more surface area to catch light creating a magnifying effect focusing light on your skin as well. The random texture in the beach sand will also give you even tan. Most sand is white in color even if not the ...


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The question is: what is the optimal way to pour the water so that it [the bottle] completely empties fastest? I conclude the aim is to have the empty bottle, not the water in another container. Solution: Create a centrifuge-like setup, bottle opening to the outside. The setup will generate artificial gravity for the water in non-inertial frame of reference ...


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Option 3: Squeezing the bottle. Of course it depends how much pressure you are able to do, the strongest you are the fastest, and if you compress the bottle in an industrial press, the water will leave in a split second without breaking the bottle (well, it gets deformed, but that was an option).


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Cut the bottle base and squeeze the bottle The air pressure has a major role to play in this situation. If you keep the bottle vertical, there wouldn't be any room for the air to move in as the water falls through which is the reason why you see turbulence and interruptions. There are various ways to tackle the issue. The best method would be to punch a ...


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What I have observed is that if we turn the filled bottle (open) upside down and plug in a straw then the water starts to flow out faster. This happens because by plugging in a straw we make a way for air to come inside the bottle and fill empty space. Another observation that I've made is that when water is flowing out of a bottle (upside down) just shake ...


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I should start with the disclaimer that I don't know the answer to this, however I have seen very similar patterns in flocculating systems and I would guess that the same principles are involved. The patterns are produced by adding a drop of pigment to a layer of slip. Both of these are colloidal suspensions. Slip is a suspension of aluminosilicate ...


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The basic problem is that headphones are heavy and asymmetric, whereas there's nothing attached to the shoelace. What this means is that the headphone - cord system can get stuck in stationary, locally but not globally minimum energy configurations: the twisting of a cord raises the energy of the cord, but the torsion resulting from the twist is not enough ...


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Is there actually any evidence that being in water increases your risk of getting sunburn? I suspect that this inference confuses correlation with cause. On brilliant sunny days you are more likely to strip off and get in the pool or go to the beach to cool down. If swimming or diving you are unlikely to wear a sunhat. More of your skin (especially the ...


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Yes. It's is not so much the water is the beach sand reflecting light back to you like a parabolic mirror. The droplets of water on your skin can form more surface area to catch light creating a magnifying effect focusing light on your skin as well. The random texture in the beach sand will also give you even tan. Most sand is white in color even if not the ...


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heres the whole way these water bags work you soak them in water first then fill them and hang them up the water inside keeps the bag wet and the outside surface moisture evaporates cooling the water inside the water is not ice cold only cool but much better than what it would be with no cooling effect at all


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As a rough estimate: we can approximate the shape of the can with a cylinder of radius $R=3,2$ cm and height $h=15,5$ cm (those are the dimensions of a Cola can). Its total area can be found by using $$A_T=A_L+2A_B= 2\pi R h + 2\pi R^2$$ which gives us $A_T$=$375,8$ cm$^2$. Assuming that water vapor condensation forms a 1 mm thick, continuous sheet of ...


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Realistically (statistically) speaking, AC is more dangerous that DC. This comes from the fact that 120/240v AC is the voltage that we are most likely to encounter - which can kill us. The DC voltage that we are most likely to encounter is 12 DC (in our vehicles), and it is very unlikely to kill us. For the case that we are just evaluating equivalent RMS ...


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Area of a base of a spherical cap of a height $h$ is $S = \pi (2Rh - h^2)$. This is the value water surface decreases as the ball dives in. This means that according to the principle of virtual work the force water sucks the ball in is $$ F_{suck} = \frac{d}{dh} \sigma S = 2 \pi \sigma (R - h), $$ where $R = 2$ cm is a ball's radius, $h \approx 1$ cm -- ...


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Water can not bear normal loads as well as oil. Water is bound to escape from high pressure bearings to lower presser places in an open lubrication loop leaving bear contacts. Water can create bubbles around cavities and corners and break the laminar flow which will compromise the separation of moving parts. Water will react chemically with surfaces. There ...


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An intuitive way of thinking about boiling an egg, is that you start a pool with a bunch of balls of yarn floating in it. Then when you heat the egg, it causes all the balls of yarn to unravel, and rather than a pool with some balls in it now it's a tangled mess of yarn. Before, each ball was free to move around as a unit, now each segment of each strand can ...


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It's definitely related to a surface tension That is correct. Surface tension means that the total surface area wants to be minimised. Although the water surfaces aren't very well drawn, the surface is slightly concave in the half filled glass, slightly convex in the brim filled glass. The presence of the ball reduces the total surface area. As a ...


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Thanks everyone for lots of good responses - I'm going to summarize them here for future convenience. It looks like there's no consensus on this issue, but here are some takeaways on two variants of my question: If the weak interaction were to suddenly "turn off" with the universe in its current condition, then solar fusion would stop and we'd all be ...


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Without the weak force, the asymmetry between matter and anti matter, on which we all depend, (as we definitely do not want any anti matter near us), may not have occured in the primordial universe and therefore would not be found in today's universe. This scenario is an extrapolation of the work of Cronin and Fitch,who found that for electically neutral ...


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I would tentatively say no. It could be a matter of geophysics. Without weak interactions there would be no weak decay of Potassium-40. This means the interior of the Earth would be cold, and as a result there would be no tectonic activity nor would there likely be a strong geomagnetic field. Tectonic activity cycles carbon and other elements. Without the ...


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Factors affect the time (i.e. from start to the time of equilibrium state where the following processes are sustainable: flame heat up wax, liquefied wax being pulled up, evaporated, wax vapor mixes with air, burn and produce heat) are followings, - size of wick (the larger, the more heat it can produce) - size of wick (for capillary flow) - wax type (...


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The answer is "no". Assume that the ground wire has a resistance of 1 ohm, and your step father has a resistance of 100,000 ohms, which is actually a bit lower than the "normal" value when measured with dry hands. This means that your step father will experience a current flow that is 1/100,000 times the current flow through the ground wire, assuming that ...


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1st- Take any beverage of choice that comes in a aluminum can/soda can flip lip profile. Aluminum is easy to bend and has a good elasticity and will not fracture and hold its shape when modified, this experiment will work with any material if it can hold shape after modification. Thin Plastic might not hold structure and other material might fracture or ...


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I can only give you a hand-waving explanation, but the fastest way to empty a bottle I have empirically found is to pour it upside down but rotate the bottle. The main problem is that the empty space above the water needs to be filled again with air which can not get through. If you rotate the bottle correctly, an air corridor inside the bottleneck opens and ...


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@tbf is right; lubrication, and tribology in general, is complicated. That's why there is that high effort to understand it and to design advanced materials. There are several phenomena that cause the friction force exist and the ones you have neglected causes that oils are superior to water in most industral applications. In dry sliding we can identify ...


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There are devices called Monochromators, which can produce narrow band illumination with pretty good accuracy, so if implemented correctly, one may measure the visual range of a person, I would believe.


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What comes to mind is separating white light (e.g. from the sun) through a prism, and using the colors in the spectrum with corresponding wavelength to determine what range you can see.


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Wow, Your question has many aspects. First, We are surrounded by electromagnetic fields. We can divide these fields in two parts 1). Ionizing fields (having wavelength ~200 nm and below) and 2) Non ionizing fields (wavelength above ~300 nm). Ionizing radiation (such as x rays and UV rays) can affect our body even when their energy density is small, because ...


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When the train moves, it displaces air in front of it and on the sides. So basically what you are hearing is the impact caused by the "air fronts" displaced by the two trains slamming against each other. You need two air fronts to hear the sound, so there must be two trains. Also, the speed must be high enough to significantly compress the air: this is why ...


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It is worth to mention two things. Sound is pressure wave traveling in air. When train is in motion, it brings motion to the air by the train. And when air velocity increases, the air pressure decreases based (can be seen in Bernoulli equation). When two trains move opposite to each other, the air flow is enough stronger if it is not doubled. The ...


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The parallel plate situation that you describe is not the typical condition encountered in practical lubrication operations. In addition to facilitating the surfaces sliding over one another, the lubricated bearing must also support a normal load. To do this, the gap between the surfaces varies with location along the bearing. For example, in a journal ...


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Why Oil is Slippery Explaining why oil is slippery requires a look at its chemical properties. First, oil is non-polar, which means it does not have a positive or negative charge. Some molecules, like water, have a “charge distribution,” which means the molecule acts almost like a battery, part of it has a positive charge and part of it has a ...


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A good lubricant tends to effectively minimize direct contact among components of any device that need it Keeping this in mind, viscosity is not the only factor involved. Grind a graphite pencil lead, and it makes a mighty fine lubricant. It might be that in the case of water placed between two surfaces, a water droplet which was supposed to act as an ...



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