New answers tagged

3

The probable reason why poeple say ice cream heats up your body is when you compare the amount of heat that it takes away your body compared to the food caloric value of the ice-cream. 100 grams vanilla ice cream is about 207 food Calories ($207 kcal$) according to this site. On the other hand, the amount of heat that the ice cream takes from the body is ...


1

I think this happens because when windows are open then there is free airflow in the room and doesn't affect the shutting of the door but when the windows are closed then there is obstruction in airflow. The pressure of air inside the room become less than the pressure of air outside the room and hence obstruct the shutting of the door in the room having all ...


0

I'll answer your question in three parts. "What is the average range of voltage in sky?" I would hope that for sunny skies, it's near zero - otherwise it'd be nothing but bolts from the blue all day long. But I assume that you're talking about the average range of voltage in regular lightning. NOAA says that we have .1-1 billion volts in lightning. "I ...


12

The diagram you drew is flat, but the solar system is not. The Moon's orbit is not in the same plane as the Earth's orbit. Wikipedia has a nice diagram: Because of this, when the Moon is "in between" the Earth and the Sun, it is usually a little "above" or "below" the Sun as well. You can observe this for yourself: one or two days after the new moon, ...


23

While excellent answers have already been provided (yes, it's Earthshine; yes, when the Moon is between the Sun and the Earth, you don't see the Moon at night, you see it from the daylit side of the Earth) given all the "artist's renderings" in the question and the answers, I thought it might be useful to include a diagram that demonstrates the actual scale ...


110

The premise of this question is wrong. If the moon is in between the earth and the sun (as shown on your diagram), and you can see the moon, then it is day, not night: If on the other hand, you are on the opposite side of the earth during that configuration (so that it is night), then you can't see the moon because the earth is blocking your view of it:


1

The moon circles around the earth, so half the time it is between the earth and the sun and half the time the earth is between the sun and the moon. Therefore also the moon rises and sets, the same way the sun rises and sets. If it's midnight (your are on the opposite site of the earth than the sun) and the moon is betweem the sun and the earth you can't ...


50

The sun doesn't just illuminate the moon directly. The moon is also illuminated by sunlight reflected from the earth. This is called earthshine. This makes the parts of the moon that face us visible even when the sun is on the other side. According to NASA, it was Leonardo da Vinci who first explained this. As an example, the brightly lit portion of ...


16

If it is really between the earth and the sun it is called a "solar eclipse" and and the moon's shadow falls on the earth at certain places, because it is not large enough to cover the whole sun except on a shadow path. A total solar eclipse occurs when the Moon completely covers the Sun's disk, as seen in this 1999 solar eclipse. Solar prominences can ...


8

The short answer: Cloudy ice is caused by gases (mainly nitrogen and oxygen) dissolved in the water that come out of solution when the water freezes. The small bubbles trapped in the ice cause the white appearance. Boiling the water removes the air dissolved in it, producing clear ice as a result. Assuming that other impurities don't produce the same cloudy ...


11

This answer was meant as a comment to @WetSavannahanimal aka Rad Vance but it is rather long and I hit the character limit. The reason for the opaque center should be due to the manner in which the water volume is freezing. Presumably the solution is not mixed and the outside freezes first forming a crystalline (ice) wall through which the gas cannot escape....


0

Pure water is transparent because it is a liquid. Objects that are not transparent either scatter light, due to difference in refractive index between air and the substance or they absorb all the photons at the wavelength you are observing. Skin for example is opaque largely due to scattering of visible light. In fact liquid water is blue if you look ...


27

I'm really winging this one because the last time I did an equilibrium calculation was 35 years ago! But I'm fairly sure of a partial answer (see discussion at end). A gas's solubility in water (or liquid generally) almost always decreases with increasing temperature. This phenomenon is explained in a way very like the explanation of the increase in ...


0

Big raindrops fall at 10 m/s. Let's say you drive a big car, with a windscreen 2 m high. Your car is also very fast, and you like driving in circles. So much so in fact that you do it at 5 rounds per second (I know, just assume it's possible). You also like rain, so you removed your windscreen, capturing all the rain that would otherwise hit it. At 5 rounds ...


0

It is pretty simple. The faster you move, the larger the total volume your windshield will pass through per unit time. You can combine your speed with the speed that the raindrops fall. The larger the volume, the more rain that you windshield passes through. The combination of your speeds combine as vectors for a total effective velocity. The ...


2

One thing everyone seems to have forgotten is the "tar" in tarmac. There is more than just friction on a race track there is also adhesion. drag strips will typically have fresh tar at the beginning and be very tacky. think of it like the tires being glued to the track both by the tar and the melted "rubber" material of the tires. the more surface area for ...


11

The claim that frictional force does not depend on area of contact is not, in general, true. It is a good enough approximation for many cases that it can be used for many real world calculation and even more back-of-the-envelope estimates, but it fails under several circumstances. Conditions for failure of the not-area-dependent approximation include (but ...


0

As @Gert says hair is made up of the protein keratin. However, even polymeric proteins are far thinner than any strand of hair, (a few nanometers across ) and thus any individual hair must consist of many millions of keratin polymers. These will be twisted and folded back on themselves to make a hair fibre. Each segment of the keratin protein polymer has a ...


0

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 ...


4

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 ...


-1

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


2

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 ...


0

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 ...


-1

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.


3

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 ...


62

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 ...


1

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 ...


2

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 ...


6

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 ...


-1

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 ...


3

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 ...


1

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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