Applies to questions related to common objects and frequently experienced effects. Typically, these questions require explaining how the laws of physics are applied to a common situation, how objects work, etc.

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10
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8answers
4k views

Why do ice cubes come out easier from top trays?

This is my "hey, I've noticed that too!" question for the week. If you stack two plastic ice cube trays with water in them in a freezer, the resulting ice cubes in the top tray will usually come out ...
4
votes
3answers
1k views

Please recommend a good book about physics for young child (elementary school aged) [closed]

I'm looking for a book that would be appropriate for an advanced elementary school aged kids (say, 6-11 YO) describing the basics of physics (or sciences in general) in entertaining way. The ...
3
votes
0answers
108 views

Can you safely draw sparks from the nose of an electrified boy?

From Purcell's Electricity and Magnetism A spectacular conclusion of one of the popular exhibitions of the time was likely to be the electrification of a boy suspended by many silk threads ...
3
votes
3answers
615 views

Is there more energy in the collapse of a cavitation bubble than the energy required to create the bubble in the first place?

The following does not include all scientific details and parameters, only a common summary of "thoughts". What is scientifically wrong with this summary? When you take your beer and tap the top ...
0
votes
1answer
375 views

Why is the optimum wheel size of a bicycle about the same as that of a car?

The optimum wheel diameter of cars and bikes appear to be roughly the same, certainly well within an order of magnitude. This is despite very different average speeds and propulsion mechanisms. Can ...
3
votes
3answers
589 views

What is the most efficient way to use hand dryer?

What's the most efficient way to place your hands under the hand dryer? Let's assume that dryer creates simple downward flow of hot air. Here are some examples:
2
votes
3answers
2k views

How much energy was consumed when we turn on/off light?

My parents told me to turn off the light when I am not using it. But I remember my physics teacher told me that the action of turning on/off a light can cause huge energy. I am wondering how much is ...
5
votes
4answers
2k views

Should I heat my room when I'm not here, energy-efficiently speaking?

I was wondering as it's getting cold : is it better for my electricity bill to shut down completely my (electric) heater during day, and to turn it on again when I come home (then it will have to heat ...
4
votes
2answers
2k views

Why are refrigerators 4 degrees and freezers -18 degrees?

I assume that the refrigerator's temperature of 4 degrees has something to do with the fact that water is densest at that temperature. Does that inhibit microbe growth? But what about the freezer, ...
2
votes
1answer
287 views

How does physics scattering experiments relate to real life? And what does the scientist gain from such experiments?

How does physics scattering experiments relate to real life? And what does the scientist gain from such experiments? I am having a hard time figuring the answer out. Please help.
2
votes
1answer
132 views

Why are bubbles formed in the empty space of soda when turned upside down?

I know this may actually be a chemistry question, but I don't know where else to ask. When I have a soda plastic bottle, I turn it upside down so the soda fills the empty space, and bubbles start ...
8
votes
3answers
461 views

What made the keys in my pocket so hot?

Not sure where to ask this question - thought you guys would probably have the best idea! Today a single key on my keychain in my pocket heated up so that it was too hot to handle and scalded my leg. ...
4
votes
4answers
2k views

How does radio receives signal from particular station?

When you tune your radio (digital or analog) to receive say 100 MHz frequency and while in the environment there are hundreds of channels everywhere around the radio. How does it chooses to receive ...
3
votes
2answers
1k views

Relating milliampere-hours to watt-hours for batteries

I've seen many batteries that are measured in milliampere hours (mAh), while others are measured in watt hours (wh). How can I convert them between each other so that I can actually compare them? It's ...
7
votes
2answers
1k views

How can rising bubbles shrink and disappear?

I was recently looking at a Wurlitzer juke box, and noticed something strange. It's decorated with liquid-filled tubes. Gas bubbles are injected at the bottoms of the tubes, and the bubbles naturally ...
2
votes
2answers
2k views

How do I join two co-axial cables?

I'm trying to join two ends of co-axial cables. I've managed to connect the two ends of copper wires but still the signal response is very low. When I try to stretch the cable signal gets good. Why ...
2
votes
2answers
279 views

Why do balls in a spinning ellipsoid move to the minor axis plane?

There is a question concerning the Physics of a small child's tall that has been bothering me for some time now. I have investigated this to a small degree, but I have not been able to find a ...
0
votes
0answers
2k views

How to determine size of a Heat Exchanger?

I am designing a Tube heat-exchanger, similar to this: My process requires water (at room temperature, 18C ~ 22C) that is being pumped out of a small tank (300 Liters) to be heated in a ...
7
votes
2answers
1k views

Infrared remote flashes blue light in camera

I know that if you held an infrared remote in front of a digital camera, it'll flash a blue/purplish light when you press the buttons. Why?
5
votes
2answers
4k views

What happens to a fully charged battery, when you continue to charge it?

If I leave my cell-phone charging the whole night, it will be fully charged after a while. What happens with the battery and the excess energy I add? Also, I noticed my charger emitting a different ...
9
votes
2answers
818 views

Why do mirages only appear on hot days?

A previous question asked why the road sometimes appears wet on hot days. The reason is that when there's a temperature gradient in the air, it causes a gradient in the index of refraction, causing ...
1
vote
2answers
2k views

Measuring the Electromotive Force and Internal Resistance of a Battery?

Here is a problem that emerged some time ago: We needed to measure the emf(electromotive force) and internal resistance of a car battery. The only instruments were voltmeter and ammeter. ...
9
votes
5answers
2k views

Why does my refrigerator door resist opening?

After closing my refrigerator's door I noticed that it's much harder to reopen it immediately, as if there's an underpressure. Only after a minute or so it opens normally. How can this be explained?
3
votes
1answer
411 views

What is the formula for the glug point?

When you pour water out of a bottle, normally you have a smooth stream. However, if you pour it too fast it glugs, which is to say, comes out in quantized bursts. What is the formula for calculating ...
0
votes
1answer
553 views

How does a table fan work?

In a table fan, the blades move around in circular way and we feel air/wind when sitting on front of it. How does this happen?
3
votes
1answer
99 views

What ring weave disposition should be the most resistant against stabbing and/or how to determine it

In a website that I am studying so I can build a Chain Mail, I have found a page featuring a lot of different Ring Weaves to build them. I want to determine which one is the best to provide ...
0
votes
1answer
88 views

Explain moving lightbulb [closed]

An acquaintance of mine, while being home alone, saw that the light bulb in the room which was hanging from the ceiling with wires having a pendulum motion which was more than noticeable. He says that ...
1
vote
4answers
6k views

domestic electric AC wiring - Live and Neutral correct or not? [closed]

On electric circuits, with $120$ or $230$ AC mains, there are the wires Live and Neutral. The wiring isn't symmetrical : following the circuit, you cannot switch $L$ and $N$. However, in Italy, ...
4
votes
1answer
224 views

What Is the Noise of an MRI Machine

What is the source of the loud noise of an MRI medical scanning machine? Is it due to some mechanical moving parts such as pumps, or is it an effect, similar to magnetostriction of superconducting ...
5
votes
2answers
319 views

Why does a firebrand glow brightest before it burns out?

I've noticed this in match-sticks, and mango wood. After the flames die out, the brand glows red for a while. The glow is brightest right before it dies out. My guess is that immediately before the ...
4
votes
1answer
7k views

Why is my tupperware sealed after heating it up in the microwave?

I had a vegetable soup in a crystal tupperware and I put it in the microwave to heat it up. The funny thing is that when I took it out, it was impossible to open it up. The lid is bent towards the ...
3
votes
2answers
1k views

Which phenomena is involved in the clothes drying process?

There's this question that has been bugging me most of my life: how is it that wet clothes left hanging to dry, get actually dry? If I get it right, the clothes are a mesh of fibers (we could assume ...
1
vote
3answers
2k views

Function of air conditioner

What i always thought that air conditioners blow the cool air without knowing that they actually take the warm air from indoor and from outdoor. But whats the point of taking air from indoor and ...
0
votes
2answers
916 views

Maximum limit on the number of paper-folds possible after tearing into halves [duplicate]

Possible Duplicate: Why can't a piece of paper (of non-zero thickness) be folded more than "n" times? On skeptics.stackexchange, there is a question on the maximum limit on ...
5
votes
1answer
2k views

Why did my liquid soda freeze once I pulled it out of the fridge and opened it?

This isn't a duplicate to "Why did my liquid soda freeze once I pulled it out of the fridge?". My question is why soda froze after it was opened. Opening a can or bottle seems to have a larger effect ...
4
votes
4answers
2k views

Does a full freezer freeze items faster than an empty one?

Let's say we want to freeze a banana. Would it freeze faster if we insert it into an empty freezer, or into one that already contains many frozen bananas?
4
votes
1answer
183 views

The feeling of fuzz on the display surface of a Cathode Ray Tube Television

I was always wondering where the feeling of fuzz comes from when touching a CRT (Cathode Ray Tube) television on its display screen when the TV is turned on. Can someone please explain why I feel ...
34
votes
5answers
13k views

Why do power lines buzz?

When near high tension power lines, particularly after a good rain, the lines themselves emit a buzzing noise. A similar noise can be heard coming out of the electric meters attached to my apartment. ...
-4
votes
4answers
1k views

Relativity in Real Life

I have no formal training at all in relativity. But I was just wondering if our perception of time is altered by different events. Here are some examples I had in mind: If I touch a stove for 10 ...
5
votes
3answers
643 views

Get an intuition for pressure values

I am currently working with pressure differences in the milibar range. However I do not have a good feeling for pressure differences. In every day life: Where does a pressure of say 100 mbar over ...
9
votes
4answers
2k views

Does it matter how you order your tug-of-war participants?

In a tug-of-war match today, my summer camp students were very concerned about putting the biggest people at the back of the rope. Is there any advantage to this strategy?
1
vote
2answers
784 views

Entropy and how it applies to everyday activities like eating food

So I was eating a plate of food one day and thought of entropy. As I understand the definition of entropy, it is the logarithm of the number of arrangements or states the object in question can be in, ...
1
vote
1answer
489 views

Paper stiffness

As piece of paper is folded and unfolded, the stiffness of the sheet may seem to be greatly increased. To those of you who don't recognise it: take a sheet of A4 paper, grasp one of the edges and ...
3
votes
3answers
3k views

Pressure inside a light bulb

It is known that nowadays most light bulbs are filled with gas in order to minimise the evaporation rate of tungsten. Is e.g. argon put into the bulb with reduced pressure, so that the glass doesn't ...
4
votes
1answer
333 views

What is the purpose of a “protect from light” warning?

Some food or medical items, like rasberry juice concentrate I just bought, have a "protect from light" warning on the label. How can light influence products like milk and what does this warning mean ...
8
votes
4answers
8k views

Why will crushing a partially empty 2-liter bottle keep the soda more fizzy?

One of the curses of 2-liter bottles is that when carbonated beverages are stored in them for long periods (i.e. days between drinks) at least the last liter ends up being flat. However, if after ...
9
votes
3answers
2k views

Why is there more steam after a pot of water *stops* boiling?

I have a pot of vigorously boiling water on a gas stove. There's some steam, but not alot. When I turn off the gas, the boiling immediately subsides, and a huge waft of steam comes out. This is ...
1
vote
1answer
135 views

Settling of rice as it's cooked

I couldn't think of a better title because I'm not sure what's going on with this phenomenon--someone who has an answer, please edit to fit this better. I noticed that when I cook rice, at some point ...
5
votes
7answers
14k views

Why won't my door close in the winter?

Please, take this question seriously, because this is a real problem to me. I have a door in my flat. A closet door, to be specific. And there is a problem with it. In the summer everything is ok, ...
-4
votes
2answers
483 views

An iPhone falling on carpet is fine, is it true? [closed]

I heard that an iphone falling on carpet would not cause damage to it, both internal and external. Any physical explanation for this?