Questions tagged [everyday-life]
Concerns the application of the laws of physics to analyze common situations encountered in everyday life.
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Given Newton's third law, why are things capable of moving?
Given Newton's third law, why is there motion at all? Should not all forces even themselves out, so nothing moves at all?
When I push a table using my finger, the table applies the same force onto my ...
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Why does holding something up cost energy while no work is being done?
I read the definition of work as
$$W ~=~ \vec{F} \cdot \vec{d}$$
$$\text{ Work = (Force) $\cdot$ (Distance)}.$$
If a book is there on the table, no work is done as no distance is covered. If I ...
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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 a magnetic field 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 ...
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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 - ...
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How does water evaporate if it doesn't boil?
When the sun is out after a rain, I can see what appears to be steam rising off a wooden bridge nearby. I'm pretty sure this is water turning into a gas.
However, I thought water had to reach 100 ...
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Why do wet objects become darker?
When something gets wet, it usually appears darker. This can be observed with soil, sand, cloth, paper, concrete, bricks...
What is the reason for this? How does water soaking into the material ...
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Cooling a cup of coffee with help of a spoon
During breakfast with my colleagues, a question popped into my head:
What is the fastest method to cool a cup of coffee, if your only available instrument is a spoon?
A qualitative answer would be ...
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Why is the return current through a printed circuit board's ground plane concentrated below the circuit trace?
The Wikipedia article on ground plane says
In addition, a ground plane under printed circuit traces [the paths that the circuit currents take] can reduce crosstalk between adjacent traces. When two ...
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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 ...
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Why does a cork float to the side of a glass?
Why does a cork ball float to the side of a glass as illustrated in the following GIF? What is the physical phenomenon behind this observation and why does it happen?
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Is electricity instantaneous?
My question is basically what exactly is electricity? I've simply been told before that it's a flow of electrons, but this seems too basic and doesn't show that electricity is instant. What I mean is ...
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Height of Water 'Splashing'
Suppose from a height $H$, I throw a ball of mass $M$ and radius $R$ with initial velocity $u$ into a pool of depth $x$ having a liquid with density $\rho$ and coefficient of viscosity $\eta$.
Upto ...
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Do low frequency sounds really carry longer distances?
It is a common belief that low frequencies travel longer distances. Indeed, the bass is really what you hear when the neighbor plays his HiFi loud (Woom Woom). Try asking people around, a lot of them ...
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Can I compute the mass of a coin based on the sound of its fall?
The other day, I bumped my bookshelf and a coin fell down. This gave me an idea. Is it possible to compute the mass of a coin, based on the sound emitted when it falls?
I think that there should be a ...
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Why do I see a saddle in this picture of a computer screen?
I am not entirely sure this is an appropriate question for PSE, however since many of you have such diverse backgrounds, I'll give it a shot.
I have noticed that when one takes a picture of a computer,...
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Why does sunset over a body of water cause a path of light stretching towards the horizon?
Have you ever notice the sunset's image in the sea? It's like long light path to the end of the horizon! I've attached a sample of this:
How can we explain this? I know that it can happen even in ...
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How does buoyancy work?
I realised, reading another Phys.SE question about balloons moving forwards in an accelerating car that I don't really understand how buoyancy works. Particularly concerning, for a SCUBA diver.
The ...
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Why do sunbeams diverge even though the sun is much more than a few kilometers away?
Consider this picture of sun beams streaming onto the valley through the clouds.
Given that the valley is only (at a guess) 3km wide, with simple trigonometry and the angles of the beams, this gives ...
user56903
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Why is filling a balloon from your mouth much harder initially?
Why is it that when you first fill up a balloon, it's hard to get air through, but after inflating it a bit, it becomes much easier to further inflate the balloon?
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Why do the big nuts always remain at top? The Brazil-nut Effect
Most of the time when I mixed different nuts in a bowl, I observed that the big Brazil nuts were always on top while the small peanuts settled near the base. No matter how you take it, if the big nuts ...
user36790
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Ice skating, how does it really work?
Some textbooks I came across, and a homework assignment I had to do several years ago, suggested that the reason we can skate on ice is the peculiar $p(T)$-curve of the ice-water boundary. The ...
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What's the difference between running up a hill and running up an inclined treadmill?
Clearly there will be differences like air resistance; I'm not interested in that. It seems like you're working against gravity when you're actually running in a way that you're not if you're on a ...
aaron
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Why do we use kilograms instead of newtons to measure weight in everyday life?
What was the reason to use kilograms to measure weight (e.g. body weight, market vegetables etc.) instead of using newtons in everyday life?
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How does light bend around my finger tip?
When I close one eye and put the tip of my finger near my open eye, it seems as if the light from the background image bends around my finger slightly, warping the image near the edges of my blurry ...
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What makes running so much less energy-efficient than bicycling?
Most people can ride 10 km on their bike. However, running 10 km is a lot harder to do. Why?
According to the law of conservation of energy, bicycling should be more intensive because you have to ...
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Why is boiling water loud, then quiet? [duplicate]
Water in my electric kettle makes the most noise sixty to ninety seconds before the water comes to a full boil. I have been fooled many times by the noisy kettle, only to discover that the water was ...
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Why do I always hear remote train horn at night?
This is definitely not an illusion, as many people have the same experience. I have usually lived in places miles away from train stations, which makes it unlikely to hear any train horns during the ...
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Why does soda fizz when it meets ice?
I read that the soda's temperature allows it to contain its $\text{CO}_2$: colder means it can retain its bubbles better.
So, why does soda fizz when it meets ice?
If anything, because the soda is ...
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Why are mirror images flipped horizontally but not vertically?
Why is it that when you look in the mirror left and right directions appear flipped, but not the up and down?
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Why does dust stick to rotating fan propeller?
Why does dust stick to rotating fan propeller?
Intuitively, most people (including I) think of the dust will not stick to rotating fan propellers.
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Why do earphone wires always get tangled up in pocket?
What is the reason?
Is it caused by their narrow shape, the soft material, walking vibration or something else?
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Why are stars white?
That is may be an easy question, but I am not a professional. The Sun is a star, and when I look at the Sun it is usually yellow. Why are stars in the sky at night white?
I suppose it could be due to ...
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Why are so many different types of objects white, yet appear gray when they are wet?
There are many things with different textures that appear white – salt, beer foam, paper, shaving cream, snow, talcum powder, white paint, etc. The most common answer is all of the frequencies must be ...
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Why do wheels appear to revolve opposite to the direction they are rotating?
When viewing cars that are driving along side of us, sometimes their wheels appear to be turning backwards even though they are traveling in the same direction as our car. Why do they look that way?
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Microwaves: why do they cook food?
I have looked up several explanations of microwaves and how they work but I am unclear on a few key parts of how they actually make the food hotter.
How I understand it now:
In addition to the light ...
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Why does paper become translucent when smeared with oil but not (so much) with water?
When I smear oil onto a scrap of paper and rub it in, the paper becomes quite translucent; but when I attempt the same with water it doesn't as much. Why?
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Does car tire pressure change with weight of car load?
Does tire pressure measured by a meter on tire gauge change with load? (I am not interested in pressure produced by car tires onto the road).
Car spec usually says "inflate to 220kPa normal load, ...
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Squinting at street lights
Simple question, I've always wanted to know the answer to this.
Why do you see a pair of lines radiating out from street lights when you squint at them? I can't think of a better way to describe what ...
user5335
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Why is the sky dark at night? [duplicate]
The question is the well-known Olbers' paradox:
If there are so many/infinite stars, in every direction, why is it dark at night? Where goes all the light we don't see?
Discussing with a friend ...
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Why does one get an illusion as moon following him?
When you run or ride bike at night if you observe the moon you feel like he moves along with you as the same speed you are going. Why?
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What causes a soccer ball to follow a curved path?
Soccer players kick the ball in a linear kick, though you find it to turn sideways, not even in one direction. Just mid air it changes that curve's direction, i.e., it swings, as footballers say. Is ...
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Why don't we see solar and lunar eclipses often?
Since we see the new moon at least once in a month when the Moon gets in between of the Sun and the Earth during the evening ( and as far as I know if this happens during the day, you'll get to see a ...
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Why does a balloon spiral in the air instead of moving in a straight line?
When an air-filled balloon is released without its opening tied up, it moves in a circular path rather than a straight line. Why is that?
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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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Why is water clear?
Water appears transparent to visible light, yet most other objects are opaque. Why is that? Is there an explanation why water appears transparent?
Is water transparent at all wavelengths, or are ...
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Why does dry spaghetti break into three pieces as opposed to only two?
You can try it with your own uncooked spaghetti if you want; it almost always breaks into three when you snap it. I am asking for a good physical theory on why this is along with evidence to back it ...
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Where does deleted information go?
I've heard that, in classical and quantum mechanics, the law of conservation of information holds.
I always wonder where my deleted files and folders have gone on my computer. It must be somewhere I ...
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If temperature is amount of kinetic energy of particles, then how can there be a cold breeze? [duplicate]
When we put hands on A/C it gives cold winds. These winds have high kinetic energy but low temperature. How ? *don't confuse with A/C being heat pump , just an example, take antarctic blizzards. I can'...
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Why won't a tight cable ever be fully straight? [duplicate]
I posted this picture of someone on a zipline on Facebook.
One of my friends saw it and asked this question, so he could try to calculate the speed at which someone on the zipline would be going when ...
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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 ...
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