# Tagged Questions

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

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### Can we detect whether food has previously been heated in a microwave oven?

An acquaintance told me that she refuses to eat microwaved food because she read that the microwave changes the molecules of the food somehow. Her statement is vague and her sources are dubious but I ...
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### Squinting at light sources

I am sure it's just your eyelashes creating a filtering effects, but if you look a a bright(ish) light source such as a lightbulb while squinting, if looks like you are seeing straight light rays ...
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### Accelerate the car by static friction

I asked this question about friction and slip ratio and now I still don't understand it Why friction is zero when wheel slip is zero? As the below graph of wheel friction vs slip ratio shows that in ...
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### Why friction is zero when wheel slip is zero? [duplicate]

From most graph, when the tire doesn't slip, then the friction is zero, for example see the below image Why there is no friction when there is no slip? As the car stand still on slope, there is no ...
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### Why does soap produce more foam when rubbed on a head with hair?

While bathing, if you rub soap on parts of your body like the chest or hand, it creates less foam. When you rub the soap for a longer time only then the foam produced will be more. But, when you rub ...
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### When I stretch a rubber band, it breaks. When I hold the broken ends together, why doesn't it join again?

The question is simple. When we join the two broken surfaces, what is it that keeps the surfaces from connecting with each other, while earlier they were attached to each other? Also, would the two ...
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### Red color has largest wavelenght and violet minimum (in the range of visible light). then why does violet light appears reddish? RED + BLUE = VIOLET [duplicate]

My question is simple. Green light is more similar to red light than violet, then why is violet reddish and green not? in the language of frequencies and wavelengths, red and violet should contrast ...
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### Why does a candle blow out when we blow on it? Our breath is 16% oxygen and only 4% CO2

Don't say that a layer of carbon dioxide covers the flame, because our breath has more oxygen than carbon dioxide. Also, our breath does not cool the flame as it is itself warm. So what is happening ...
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### Order of magnitude estimation for some intriguing questions

The physics TA showed us a few examples in which one can estimate many things from first principles, sound logic, and scaling arguments. This led usually to understanding of why some numbers have the ...
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### Why do floating objects attract? [duplicate]

Objects floating on the surface of calm water seem to be attracted to one another and tend to come together in a drift. Is this attraction like gravity?
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### Mirror Transportation

Why do people transport mirrors in inclined position? I frequently find people carrying mirrors in slant position on mini trucks.I guess it has some advantage of carrying them without breaking,and I ...
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### Is preheating plates in microwave dangerous? If so, why?

My understanding of microwaves was that due to the high frequency they are easily absorbed into any material. The more "loose" the material, the easier the absorption. I know it's dangerous to let ...
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### Refrigerator cooling power usage

I have a refrigerator, that makes a lot of noise, and we have therefore set a time on it will limit the run time to when we are not at the office. But this is where our discussion begins, should we ...
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When my hair gets long I start doing a little flick of my head occasionally to get my hair out of my eyes. This grows into a habit though, and for the first few days after cutting my hair I end up ...
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### Is it possible that a battery goes flat faster in a cold environment?

I own an old iPod Classic with original lithium-ion polymer battery and I use it primarily while running. Recently I discovered that when a temperature outside is low, usually below 5 C degrees, the ...
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### Why does my body create interference with my clock radio while in bed?

I typically listen to NPR in the morning from a clock radio next to my bed. There are days when just moving my body, even my arm or leg, is enough to cause interference with the radio to dramatically ...
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### Why does my kettle only make a noise when it is turned on

Almost as soon as I turn my kettle on it starts to make the familiar kettle noise, yet very shortly after turning off the power the boiling noise stops and the kettle is totally silent. The ...
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### Why does a remote car key work when held to your head/body?

I was trying to unlock my car with a keyfob, but I was out of range. A friend of mine said that I have to hold the transmitter next to my head. It worked, so I tried the following later that day: ...
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### What are circles on broth (eating soup) surface?

Think about broth in the soup, usually it has circles on its surface. What are their properties? Why there are many of them (not a few big blobs)? Are they depended on liquid's temperature? What needs ...
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### Why is a wine glass shaped the way it is? [closed]

Why is a wine glass shaped the way it is? And why are there different shapes for different wines? Is this a tradition, or is there any scientific reason behind it?
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### Rotation motion like the number 8

I'm a college student majoring in culinology and I'm trying to find out the reason or method of the number 8 motion. Responses doesn't have to be in culinology examples, but that would be a great help ...
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### How does the magnetic field get induced in car's tire?

I was amazed to see how my car's tire started attracting the nuts and bolts, how in the world did it induce the magnetic field? Never heard of such phenomena!!!
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### (Why) would unmaintained water heater use more electrical energy?

I'm specifically thinking about lime/sedimentation at the bottom of water heater, and calcification of heating elements (and not possible thermal insulation deterioration). It is very often claimed (...
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### “In-head” sound intensity with and without earplugs

When you bite something in two pieces, e.g. a piece of hard candy, you hear the sound through two sources: vibrations in the air, entering your ears from the outside and internal vibrations in your ...
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### 'ting' 'ting' sound from a tube-light?

Whenever I light up a tube-light it makes 'ting' 'ting' sound every-time it blinks. I am talking about this tube-light Why is it so? I think its because of sparking(inside glass tube) ...
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### Can walking provide electrical energy?

This is more of a theoretical question, but is it possible to convert the energy you use to walk into electrical energy to say, power a light bulb?
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### How to simulate a full-suspension bike? [closed]

As a fun project, I would like to roughly simulate the suspension operation of a full-suspension mountain bike. This is not another one of those "How does a bicycle stay upright?" questions. Follow ...
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### Why does a car bonnet (hood) rise when you connect the clutch with a brake on?

Is the rotational force to overcome the brakes moved to the opposite effect of moving the car chassis, until the brake is released?
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### Can a car skid while moving in a circle? [closed]

How can a car skid if it is moving around a circular road? It is understandable that it can topple but I feel it impossible that a moving car can skid. It is hard to imagine that a car would skid ...
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### Why does the Sun turn red near sunset?

At daytime the Sun's light is yellowish if not near white. Why when the Sun starts to go down that it's light turn more red. I don't think the earth's rotation is so rapid to cause a red shift. Why ...
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### How do speakers play sounds with multiple sources?

I know that speakers produce sound by creating a pressure wave, but I don't understand how when they play music or games you can hear the different sources. I guess what I'm asking is how do they play ...
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### The physics of breaking eggs [closed]

I have to to write an 4000 word research paper for my IB diploma in high school. It is called the extended essay. I was thinking about writing on the physics of breaking eggs. I came up with the idea ...
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### How much weight can a person carry to avoid being blown over by wind?

I wonder if there is a certain amount of weight that I could carry in a rolling bag to help prevent me from being knocked over by the wind. I have balance problems and some lack of muscle strength in ...
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### Why is there water coming out of a car’s tail pipe?

I notice yesterday that my neighbor’s car had water coming out of the exhaust pipe in the morning. My first response was since the hot exhaust is hotter than the cold tail pipe, heat is transferred ...
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### Why does a bottle shrink when you pour hot water in it?

I think the title says pretty much. Last night I poured hot water in a half full bottle of water and closed the cap. The bottle immediately shrunk. Why? My girlfriend suggested that the hot water has ...
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### Velocity of hitting the ground when falling forward

A friend of mine fell while he was snowboarding which led to a discussion. He mentioned that, in general, if your center of mass is traveling at a certain velocity, and you fall forward, your head ...
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### Golf: spin direction resulting from striking out of the toe

If a golf club strikes the ball out of the centre of the club face with the club path on the target line through impact, and the face square to target, the ball will move towards the target with no ...
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### Why do canvas water bags and doors expanded when wet?

I recently asked a question on a canvas water bag and I realized that there was something really interesting that I didn’t understand. When a dry water bag gets filled, it leaks a lot of water; ...
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### Branching lemon drop “smoke rings”

This might be hard to ask, but here goes nothing. I recently poured a cup of water into a black coffee cup. There was a light source--not very bright--above the cup. Anyways, I was squeezing a ...
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### How does a canvas water bag cool water?

I was reading about this water bottle by Botl that behaves like a canvas water bags to keep water cool. I found out that this idea is an old idea and cars would drive with water bags in front as shown ...
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### Does humidity make cold air feel colder?

I sometimes hear stories where people compare their feelings in winter in different places in the world. It goes like in city X the temperature was the same as in city Y, but the humidity made me ...
3k views

### Why it is difficult to drink tea with a straw?

It is easy to drink cold drinks, soft drinks with straw but when I tried to drink tea with straw then that was very unpleasant and even for time I lost the sense from my tongue. My question is why it ...
1k views

### Does car lose kinetic energy when turning?

I am writing simple car simulation. Assume non friction, then in straight line the car doesn't lose speed. But what if the car is turning, there should be some kinetic energy loses to change the ...
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### Why does a cooling motorcycle make popping noises?

I was sitting in my parked car tonight when a Harley-Davidson motorcycle parked next to me. With my window down, I could hear that as the motorcycle was cooling down, it was giving off some type of “...
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### Can we create invisible things?

We are able to see this beautiful world because of light. When light gets reflected from the object, the reflected light enters our eye retina and thus we are able see that particular object from ...
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### Would it be possible to distinguish rap and singing from just seeing the soundwaves?

For any person even remotely familiar with music it is obvious that rap and singing are easily distinguishable (save for some interesting mix styles). This means that there must be a clear difference, ...
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### How do I figure out the momentum of a water balloon when it reaches the person I am throwing it at?

Recently an experiment was performed in which myself and a partner filled a water balloon and threw it back and forth at each other without breaking it. We gradually increased the distance at which it ...
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### Why do shadows from the sun join each other when near enough?

I was laying on my bed, reading a book when the sun shone through the windows on my left. I happened to look at the wall on my right and noticed this very strange effect. The shadow of my elbow, when ...