# Tagged Questions

Concerns the application of the laws of physics to analyze common situations encountered in everyday life.

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### Why do clouds form in lumps?

What forces drive the water vapor to form the shapes every child draws? Why isn't water vapor forming an uniform mist layer consistently (which it some times does)? I have two general ideas how this ...
329 views

### In a large city how much hotter on average is it outside due to the air conditioning of all the buildings?

Title pretty much states the question. How much hotter do air conditioning units make it outside in a large city like NYC, Chicago, etc?
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### A book sits on a table. What is the net force of air pressure?

An elementary problem asks, A book is at rest on a table top. In what direction is the net force of air pressure on the book? Is this a meaningful question, and if so, what's the answer? If ...
3k views

### Why does a cork float to the side of a glass?

What is this physical phenomenon and when it's happen ? Please take a look at this picture: Notice: This is a cork ball attracted to sides of a glass of water
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### Why does wet skin sunburn faster?

There is a popular belief that wet skin burns or tans faster. However, I've never heard a believable explanation of why this happens. The best explanation I've heard is that the water droplets on the ...
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### Balloon Inflation

I am planning to use an air compressor to inflate a rubber balloon. I need to size the compressor for inflating the balloon, but for sizing the compressor I need the pressure required to inflate the ...
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### What force does bathroom scale measure?

When you stand on a bathroom scale, I know that the force displayed is the normal force. Since it is the normal force, then technically the force displayed would actually be Fg= (mass)(acceleration) ...
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### Where does the light go when I turn off the light switch?

As above... Surely it must go somewhere? My child asked me this question and it was a difficult one to answer.
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### How can you weigh your own head in an accurate way?

I read some methods but they're not accurate. They use the Archimedes principle and they assume uniform body density which of course is far from true. Others are silly like this one: Take a knife ...
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### Calculating Mass for a Reduced Trajectory while Keeping Projectile Force Constant

Apologies if this is not a research-specific question, but applied mechanics. A firefighter has to pass a test in which he is to throw a medicine ball a certain distance. The ball is thrown at a 45 ...
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### How do they measure the rotational speed of cricket balls?

The 2013 Ashes series (a cricket thing between England and Australia) are underway as of today and it seems they have a new (to me) gimmick. It appears that they are now able to measure almost ...
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### Why can't I slap an insect into unconsciousness?

So it is summer, which means I have to deal with insects. Today one has made it into my room and while I tried to work this insect was constantly in my face, which caused me waving my hands in the ...
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### Movie airplanes and suction

Having watched a recent action movie (with zombies in it) I wondered whether the suction from a hole in the airplane's hull would really be able to rip out luggage, persons and even seating benches. ...
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### Canonical everyday-life example of a technology that could not work without humans mastering QM in analogy to the application of GR in GPS?

The GPS is a very handy example in explaining to a broad audience why it is useful for humanity to know the laws of general relativity. It nicely bridges the abstract theory with daily life ...
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### Extreme heating by Sun on Earth- Can eggs be fried?

Will it be possible to fry eggs in Sahara desert by just keeping them under the sun? If so, then will the radiated eggs be any different? Or will we have to use the solar cooking concept to some ...
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### Why do we feel a sudden chill?

When we are in a room, especially in some old houses, we feel this sudden rush of cold air. How does a strong air current arise and pass away so quickly?(lasts for about a second) I know air-currents ...
1k views

### Are these sunglass lenses linearly polarized or what?

This is a difficult question to phrase, so please bear with me. I found some cheap sunglasses and pulled out the plastic lenses which are polarized. For clarity, I have labeled them as lens-1 and -2 ...
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### How does sun light after it has passed window's pane still heat me up?

I believe it is so because most of photons' energy has successfully passed the glass. But is it so? And how can I roughly estimate part of light's energy which will pass obstacles like glass? And how ...
2k views

### Are two thin blankets significantly warmer than a single thick blanket?

Almost every source I can find online maintains that two 0.5 cm blankets are significantly warmer than a single 1cm blanket due to air trapped between the thin blankets. However, the thermal ...
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### Why does water freeze at $0~^\circ\text{C}$ while poultry freezes at $-2.2~^\circ\text{C}$?

We all know the freezing point of water is $0~^\circ\text{C}$, however correct me if I'm wrong, but I believe the freezing point of poultry (which I'm guessing means water in poultry) is ...
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### How fart is transported through air?

As we know diffussivity of gas is really slow (e.g. $\require{mhchem}\ce{O2}$ and $\ce{H2O}$ in the air are respectively $0.176$ and $0.282 ~\text{cm}^2/\text{s}$). here is a example to specify how ...
7k views

### Does ABS shorten stopping distance of a car?

ABS, from German Antiblockiersystem, is a device put in almost every new automobile. The web has lots of explanations about the system, how it works, but I don't understand how it shortens the way of ...
5k views

### What part of the fan blade actually does the noise generation?

I'm trying to identify the sources of noise in spinning fan blades and what causes them. Is the noise only generated by the lead edge of the blade 'cutting through' air? and different parts of it ...
2k views

### Floating a ping pong ball in the air just using a pen!

Caution: Apparently this problem is harder than it seems! There is a well known phenomena, which I first learnt about when I was a 10 years old kid. You can levitate a ping pong(or whatever ...
267 views

### Increase in cloth's mass

When we iron our clothes does the mass of the cloth increase, since energy transformation and transfer happens, Einstein's energy mass relation comes to action and causes increase in mass. Am I right ...
150 views

### Heat preserving performance of container relative to content

This question has been addressed in the case of a thermos bottle: Performance of a thermos bottle relative to contents I am asking the question again without the hypothesis that it is a thermos ...
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### Why do some air-conditioned stores blast you with jets of air as you enter?

I went to a grocery store on a hot day that was very well air-conditioned, and I noticed as I went through the open entrance that there seemed to be a very powerful downward air current right at the ...
2k views

### Why do objects sometimes fall on their own?

I have observed sometimes that when I keep some objects precariously balanced, for e.g. some objects in a cupboard, they seem quite stable at the time when I place them there but after a certain ...
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### Why is the summer, in the temperate latitudes, in average, hotter that the spring?

It is common knowledge that the transition from the Spring to the Summer season occurs in the Summer Solstice when the "Sun reaches its highest excursion relative to the celestial equator on the ...
1k views

### Performance of a thermos bottle relative to contents

I'm not a physicist but I majored it at high school (a long time ago) and I study university math. Me and my roommate discussed whether the performance of a Thermos bottle is influenced by how full ...
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### Is an ice globe the worst possible way to cool a drink (with ice)?

Given an alcohol solution and a mass of ice in whatever shape you like, is shaping it into a sphere the worst possible way to cool your drink without diluting it? If the ice starts off at a sub-zero ...
4k views

### Does a car consume more fuel when it's raining?

Yesterday my wife asked me that question, and I couldn't answer. Consider a car, in a sunny day, and that is consumes x gallons per mile. Considering that everything is equal, except that it's ...
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### Why do baked goods “fall” if exposed to sudden cooler air?

This is a know rule when baking: Don't open the oven until your cake is finished, otherwise it will "fall". Why/how does this happen?
8k views

### Is it possible to generate electricity using a water tower?

Is it possible to build a water tower that will provide enough pressure to run an electricity generator? A water pump can be used to send water up to the tower. The water pump can be powered by solar ...
432 views

### 6 Story Building Swaying, Normal? [closed]

Preface: I'm currently sitting at my desk on a 5th floor in a South Florida office building, as I was earlier this morning when I felt the building sway slightly. It wasn't continuous and the ...
686 views

### Ringing sound when you flip a coin?

When you flip a coin, you hear a ringing sound. I know that the source of the sound is the thumbnail hitting the coin, but it seems to be filtered by the spinning of the coin. Specifically, the faster ...
5k views

### How can Magnets be used to pick up pieces of metal when the force from a magnetic field does no work?

I learned that the force from magnetic fields does no work. However I was wondering how magnets can be used to pick up pieces of metal like small paperclips and stuff. I also was wondering how magnets ...
3k views

### Why does the Sun feel hotter through a window?

I have this big window in my room that the Sun shines through every morning. When I wake up I usually notice that the Sunlight coming through my window feels hot. Much hotter than it normally does ...
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### Why two balls of different mass dropped from the same height falls the ground at the same time? [duplicate]

When two balls of different masses, thrown from equal height they reaches the ground at the same time. Can anyone explain this in terms of laws of Physics(or with mathematical equations)?
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### Optical illusion of car wheels, speeding up [duplicate]

Perhaps it is some free moving spinner attached to the wheel, but as opposed to this question: Why does the wheel of a car appear to be moving in opposite direction? I have seen car wheels that appear ...
649 views

### What exactly heats a pool of water on a sunny day

On a sunny day an outdoor swimming pool will heat up fairly quickly. My question is, what is the exact mechanism for this and can we put numerical figures on it? Given that water is clear and ...
436 views

### Why do ice cubes make a cracking sound when placed in fizzy wine (Prosecco)?

When placing ice cubes in a fizzy drink such as Prosecco, ice makes a cracking sound, after which the fizzy bubbles more than usual. What is the physics of this phenomenon?
8k views

### Is play-dough liquid or solid?

At room temperature, play-dough is solid(ish). But if you make a thin strip it cannot just stand up on it's own, so is it still solid? On a more general note, what classifies or differentiates a ...
1k views

### How hot does the tip of a pencil get while writing?

When writing with a pencil, there seems to be quite a lot of friction - which seems like it would induce heat. How hot would the tip of a #2 pencil get writing on normal copy paper?
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### How does the boiling time depend on the number of eggs

My nephew showed me an exercise from his school-textbook about boiling eggs. Here is the exercise (translated from german): To make one hard-boiled egg in a pot of water one has to put it for 8 ...
4k views

### How does a sponge “suck” up water against gravity?

If I take a sponge and place it in a shallow dish of water (i.e. water level is lower than height of sponge), it absorbs water until the sponge is wet, including a portion of the sponge above the ...
150 views

### Cycling down a mountain

I am Dutch, so I cycle a lot, hence the following question. Say I am standing at the top of a mountain on my bicycle. I have an amount of energy $E$ available. Say that after the slope of the mountain ...
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### 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 ...