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

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6
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4answers
5k views

How do blankets keep you warm?

I heard a famous physicist (was it Feynman?) argue that blankets do not keep you warm by trapping heat but by trapping air next to the body. Is this true?
1
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0answers
35 views

Thermodynamics: Apartment Airflow: What Am I doing wrong air

Our apartment is a sauna. But sometimes it's much much hotter inside the apartment than it should be (night time it's 68 degrees outside but thermometer still says 90 inside!). I have 2 fans, one ...
1
vote
1answer
185 views

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 ...
42
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5answers
3k views

What causes this pattern of sunlight reflected off a table leg?

My friend noticed an interference-like pattern around the table leg. However, we do know that interference patterns of sunlight produces rainbow colours. What seems to be happening here?
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2answers
94 views

Unusual phenomenon from fluorescent lightbulb

Next to my bed I have a fluorescent desk lamp. One night, after I had turn off all the lights in my room, I grabbed my blanket from the other end of the bed. As I grabbed the blanket, one end of the ...
12
votes
1answer
471 views

Why can I turn light red or blue by holding my finger up to it?

This is a difficult phenomenon to explain. Imagine you have an opaque object partially covering a very bright light source, for example, an object held up against the sky. The left hand diagram is ...
45
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4answers
3k views

Why do some location on Earth have only one tidal maximum per day instead of two?

Most places in the ocean have two high tides and two low tides per "day" (~25 hours). But I remember reading that some locations only have one of each per day. This answer has some great explanations ...
55
votes
7answers
7k views

How did my candle wax crawl up the sides of the jar?

I have an Ikea candle which has sat on my bookshelf in the sun for >5 years. Aside from an hour or two shortly after I bought the candle, I have not burned the candle regularly (in fact, the wick is ...
131
votes
7answers
18k views

Does Earth really have two high-tide bulges on opposite sides?

The bit that makes sense – tidal forces My physics teacher explained that most tidal effect is caused by the Moon rotating around the Earth, and some also by the Sun. They said that in the Earth and ...
1
vote
1answer
70 views

How does GPS on an airplane report a 100 km error?

On a flight across Europe, I took my iPhone out to see if the GPS can find my position. I was sitting away from a window, so reception would have been bad. I wouldn't have been surprised to get no ...
12
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5answers
9k 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?
7
votes
1answer
19k views

Do we have theories about why gravity exists/how it works?

For years I have been very fascinated by the "mystery" aspect of gravity. Functionally, we understand it for our applications, but in my (limited to my 3 quarters of undergrad general physics) ...
15
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4answers
3k views

If we feel it's hotter when humidity increases, then why do we feel it's colder when inside water?

When the humidity in the air is high, we sweat more and feel it's hotter than when the humidity is lower. So why don't we feel it's hotter when we go inside water, where the water content is much ...
-1
votes
1answer
45 views

Why can't you ride a bike with a fixed handlebar?

I tried one time, as part of an experiment, to ride a bike with a fixed handle bar. Impossible. So, in any case, our movements made with the handlebar helps us in not falling down. I can feel kinda ...
0
votes
1answer
22 views

Spin on the rack

Bike mounted on hitch rack. Why wheels spin constantly while I drive? I can't find anything on the internet. The kids in the other cars love to watch them
5
votes
1answer
77 views

If a high speed car or train enters a tunnel, will the aerodynamics effect slow it down and hence requiring more energy to maintain speed?

Speed and distance are two main determinants in this question. A slow moving vehicle or train entering a tunnel is unlikely to be affected by the presence of solid stationery object covering them. But ...
5
votes
2answers
1k views

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 ...
4
votes
1answer
86 views

Why do I spill lesser water if it's hotter?

If I pour water in a glass to make a cup of tea, I noticed that if the water that comes out of the kettle is very hot, almost no water is spilled. If the water is cold though, much more water is ...
3
votes
2answers
120 views

How much money can I save on gas by losing weight?

I read somewhere that if you carried around a penny in your car, over the lifetime of the car, you would end up paying an extra penny in gas than if you weren't carrying that penny. I was wondering ...
0
votes
2answers
55 views

Why do UV lamps look purple?

UV radiation isn't visible to the human eye, so how come we can see it as a purple/violet light from a UV lamp? Is it just because the lamps aren't perfect and end up emitting some light at a higher ...
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vote
0answers
30 views

What is the explanation of the glory (optical phenomenon)?

Yesterday, I took the following picture. I was looking downwards from within an aircraft and I saw the 'glory' around the shadow of the plane on the clouds below. Wikipedia has an entry on the ...
0
votes
2answers
734 views

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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1answer
168 views

Is putting a charged balloon up to a neutral wall polarization AND temporary induction, or just polarization?

Is putting a balloon that is charged up against a wall and having it stick polarization AND charging by temporary induction, or just polarization?
5
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0answers
56 views

When beer tapping, why does only one of the beers foam up?

In the paper Physics of beer tapping the author go through an explanation of the phenomenon of beer tapping, i.e. the foaming up of beer in glass bottle after it has been hit at the top of the bottle ...
17
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2answers
2k views

Why is paper more frangible when it is wet?

My four-year-old daughter asked me why paper tends to fall apart when wet, and I wasn't sure. I speculated that the water lubricates the paper fibers so that they can untangle and separate more ...
4
votes
1answer
48 views

Breaking strength of wet paper/cloth

In the Hollywood movie, Shanghai Knights (pardon me for the non scientific citation), Jackie Chan states that 'wet cloth' does not break easily. How true a fact is this ? We know from common ...
4
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1answer
197 views

energy efficiency - dryer vs hang+dehumidifer

When I have wet clothes coming out of the washing machine, I can either tumble-dry them in an electric clothes-dryer, or I can hang them to dry. But I can only hang them in a basement. The basement ...
3
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1answer
57 views

Why is it easier to remove stains with water?

And I don't mean stain removers, but literally tap water. See here's the thing, you can't remove a stain without some sort of friction, and water reduces friction. Yet if I say, spill some coffee and ...
2
votes
2answers
78 views

How do ceiling fans cool or heat?

Why does a ceiling fan blowing air downward cool in the summertime: whereas a ceiling fan sucking air upwards heats in the wintertime: ? Why isn't it the other way around?
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0answers
38 views

Why does a fan blade appear to spin backwards when spun really fast?

This a phenomenon which I notice everyday but never really took an interest in. Why does a fan (or any other rotary object), when spinning really fast, 'appear' to slow down, upto a certain rpm, then ...
5
votes
1answer
68 views

What causes the buzzing sound when the electricity changes into heat?

When I turn on any kind of electric heating (kettle, cooker, heater, ...), it keeps producing a constant buzzing sound. What is the exact cause of that sound? Do the electrons of the electric ...
-1
votes
3answers
62 views

How do Calories (kcal) relate to watts?

In thinking about exercise and "burning calories" it occurred to me that there should be some fairly intuitive correlation between the biological energy conversion going on in a person's body with the ...
53
votes
3answers
9k views

How is 6W equivalent to 40W, as claimed by adverts for LED light bulbs?

Every advert I come across for LED bulbs advertise them as the equivalent of a higher W incandescent bulbs. This makes no sense to me, if the room requires 40W to lighten it up then it'll always ...
3
votes
2answers
44 views

Creasing of a material at the molecular level

What exactly happens when a material (particularly paper or even cloth or a metal) is folded to form a crease? Why is it that a creased material tends to retain form, while a lightly folded one, ...
2
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0answers
50 views

How fast should 6 liters flow out of the sink through a 6cm pipe?

I had 6 liters in the sink when I pulled the plug. It took the water about 30 seconds to get through a pipe which has about 5cm in diameter. I think the pipe might be blocked a bit, causing it to have ...
10
votes
5answers
2k views

Milk or sugar first to maximize temperature of a hot cup of tea?

If there is a hot cup of tea and we were asked to add milk and sugar, which mixing order would make the hottest tea? I personally think that the order doesn't matter, since sugar wouldn't change the ...
64
votes
8answers
76k views

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: ...
26
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6answers
5k views

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 ...
6
votes
1answer
99 views

Why do headphones tangle themselves whereas shoe laces untie themselves?

Why do headphones tangle themselves whereas shoe laces untangle or untie themselves? Why aren't we using the phenomenon to create headphones that tangle less and shoe laces that untie less?
7
votes
1answer
724 views

Why do flat cords tangle less in my pocket?

We've all experienced this: put a pair of earbuds in your pocket, and when they come out, they're a tangled, knotted mess, cf. e.g. Why do earphone wires always get tangled up in pocket? However, you ...
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vote
4answers
5k views

Why does squeezing a water bottle make the water come out?

This seems natural, but I can't wrap my head around it when I think about it. When I squeeze an open bottle filled with water, the water will spill out. When I squeeze a bottle, the material ...
1
vote
4answers
94 views

Why adhesion is stronger at faster peeling rate?

Adhesion is strong at fast peeling rates and weak at slow peeling rate (paper, video; Newtonian adhesive, non-Newtonian adhesive?), i.e. it is rate-sensitive. Why? (source: Meitl et al.: thanks to ...
8
votes
6answers
16k views

Why does higher acceleration minimize a car's fuel consumption?

I generally try to optimize my car's fuel consumption when driving, using my car's real-time MPG gauge and average-trip MPG indicator. Until recently, I believed the slower the acceleration, the ...
47
votes
2answers
8k views

Why do I see better under water using swimming goggles? [duplicate]

I am myopic (I don't really know if this is relevant or not) and I usually swim without contact lenses. My vision is clearly better underwater when I am using swimming goggles. I have tried to ...
0
votes
1answer
43 views

Is it scientifically possible to stop a screens polarization by adding a layer? [closed]

Back story: At work we deal with confidential data, however our desk layout does not allow for screen privacy. We do not a privacy screens and are not allowed to take apart our screens. In searching ...
2
votes
2answers
3k views

Is squared motor gearbox ratio proportional to inertia ratio?

I read an interesting article http://m.machinedesign.com/news/motor-sizing-made-easy It is very interesting, but I can not follow the 2nd last paragraph. I don't understand why it is true. ...
22
votes
5answers
84k views

Why is AC more “dangerous” than DC?

After going through several forums, I became more confused whether it is DC or AC that is more dangerous. In my text book, it is written that the peak value of AC is greater than that of DC, which is ...
3
votes
2answers
283 views

Why doesn't a glass french press shatter when boiling water is poured in?

When I was little, I accidentally shattered a glass cooking instrument due to applying far too drastic a temperature change to it. Since then, I've been a bit afraid of doing it again. Of late, I've ...
0
votes
1answer
52 views

Hard drive disk seems to “move” its weight when running

I have an external box for hard drives and plugged a broken hard disk to it. Then I turned it on and took it in hand. Now, if I gently tilt and turn the box on its axis, the weight seems to "go" in ...
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0answers
22 views

Optimal two-stage warming up of a bottle of baby milk

Here's a common two-stage method to warm up a bottle of baby milk to avoid uneven milk temperature: 1) Heat up a bowl of water in a microwave oven. 2) Put the bottle into the bowl of heated water to ...