Questions tagged [everyday-life]

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

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Why do two blurry shadows, when brought close to each other, appear to “bulge” and merge?

I have recently noticed that when two objects with blurry shadows cast by the same light source are brought close to each other, their shadows appear to merge in a way where one shadow appears to &...
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1answer
24 views

Why do colours change in water

I was doing my swimming rounds, when it turned dark, so the pool management turned on the lights. The lights were actually yellow in colour, but they appeared green if I moved far away from them ...
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1answer
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What causes pressure buildup in a cooling teapot?

Most teapots have vent holes to let steam out (and also to let air in when pouring the tea, but this is irrelevant to this question). If the vent hole is blocked, pressure starts building up in the ...
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Physics of ice around: Breaking the Ice

I was removing ice on my driveway and had a very hard time. And I am wondering what are the factors that determines the hardness of ice, and also the stickiness. one thing that I noticed about the ...
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25 views

What amount of force does the average person exert when hammering a nail into an object/concrete? [closed]

I am designing a long reach hammer that can pile nails into concrete that's used for reinforcement and formwork for my senior design project. I just need to know how much force one exerts with a ...
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A day with $c=500$ Km/H [closed]

I was reading paradoxes and was doing some problems with unexpected answers on Special relativity. And I find special relativity to be crazy. Sometimes It's hard even to believe these things due to ...
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2answers
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Why does pressure in a thermos increase after shaking up hot water and soap?

Whenever I wash my thermos, I put hot water and then some soap in; then I seal the one end with my hand or use the lid. After shaking it up, if I slowly remove the lid or my hand, it expels a little ...
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2answers
34 views

Is it true that a pair of open windows create a strong continuous “draft” wind?

A common belief is that opening two windows or doors inside the home can create a strong and steady flow of air (a "draft") that a single window would not create. This seems somewhat ...
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7answers
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Why does water cast a shadow even though it is considered 'transparent'?

If you pour water from a container, the flowing water stream seems to cast a shadow. I am not sure you can call it a shadow, but it definitely is not letting all light through it. How is this possible ...
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3answers
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Why is mist gray but water clear?

I was walking outside one cold afternoon with my mask on and my glasses began fogging up. The mist was initially gray. I kept walking without cleaning my glasses and eventually enough mist collected ...
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1answer
84 views

Why don't we burn ourselves when we speak?

In this post we learn that sound transfers a lot more energy than heat across the medium, so why don't we burn ourselves when we speak by generating sound? Does sound reflect more easily than heat?
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1answer
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Strange patterns on computer screen [duplicate]

So I happened to capture this really cool picture of a desktop screen taken through a mobile phone camera. I hope you can see those stripe-like patterns which have appeared in the photograph, but ...
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4answers
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Stood in front of microwave with the door open [closed]

I was cooking something in the microwave and opened the door early to check on it and the microwave didn't stop. I didn't realize this for a few seconds and when I did I shut the microwave off but I'm ...
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How would a small desk fan improve the air flow of a room?

Say one were sitting in a room with poor ventilation. If wind doesn't rebound off of surfaces, how would a small desk fan alter the airflow of the room?
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1answer
57 views

Why does mist on glasses disappear when you go back outside in freezing weather?

This evening after a walk in the cold weather, about -5 degree Celsius, my glasses were misting up when I got back into the warm house, about +20 degree Celsius. However, shortly after I went outside ...
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3answers
84 views

Why is the center of a torch beam visible even through an opaque body like my finger?

I have noticed that my finger never seems to completely block out the light of a torch beam as the center (brightest part of the torch) would be visible through the shadow of my finger. I thought it ...
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7answers
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In a microwave oven, why do smaller portions heat up faster?

Sorry for brevity, but what is the exact physics explanation of why smaller quantities placed inside a microwave oven heat up faster than when you place a larger quantity of a similar material inside?
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1answer
22 views

Electric swatter working when it is off

When I switch on a fly swatter for some time, then turn it off and touch it with a conductive material(such as a pencil), I get a momentary spark. The spark is not continuous that I get when the ...
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8answers
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When snow falls, temperature rises. Is this due to entropy?

A friend of mine told me that temperature rises when snow falls. And this is because condensation of water in snowflakes reduces entropy and the temperature of the air rises to compensate for this. Is ...
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3answers
195 views

Why do water drops make a louder sound when they land on a bucket , when compared to a solid floor?

I noticed this yesterday in the shower and my physics sense tingled. well im here now !
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0answers
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Why do the horses mechanical efficiency seems low relatively to that of human cyclists? [closed]

According to this article a horsepower is equal to the average power production of a horse over an extended period of time. An elite cyclist can produce about half of horsepower over an extended ...
12
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1answer
293 views

What is the purpose of the ink delivery disks found in most rollerball pens [closed]

See picture. In most rollerball pens there are those peculiar looking disks near the nib, the purpose of which I have not yet figured out, apart from being some kind of ink reservoir/flow control. ...
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1answer
47 views

How does pitch change when sound velocity change?

The hot chocolate effect makes the pitch of sound of hitting a coffee mug lower when you stir the liquid within. The explanation is that you lower the pitch because velocity lowers inside the bubbles ...
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5answers
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How does rubbing soap on wet skin produce foam, and does it really enhance cleaning?

We tend to rub soap after applying it to the skin. I found it interesting that the mere act of sliding our hands on the wet skin surface produces millions of air bubbles in the liquid, that later ...
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1answer
51 views

Why are the Earth and Moon so different?

The suggestion was made that the Earth and the Moon are two parts of a once whole object. If that is true then they must share the same basic composition. They also receive fairly similar amounts of ...
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1answer
19 views

Keep flow rate constant from a drip container

I will be using an elevated container attached to tubing with a ball valve on the end to drip a liquid into my saltwater aquarium to help with coral growth. Conceptually it will be similar to an IV ...
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5answers
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Why do wet plates stick together with a relatively high force?

When I wash up plates and don't dry them right away and place on top of each other, they seem to stick together with a relatively high "force": i.e. when I try to pick the top plate hours ...
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3answers
70 views

Why are infrared images not great?

Why are infrared images not great? Simply googling infrared images, and looking at pictures of things like streets, people, animals, etc. . . I can't quite pin ...
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2answers
58 views

Why does falling water become less and less focused as it falls down?

So, I was observing my water purifier fill up my water bottle and I noticed that the beam of water coming through it became less and less focused as it falls down more. Now, I do understand the ...
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1answer
28 views

Understanding water flow in a fertilizer injection system

I recently set up a small EZ-Flo fertigation system. This is a tank full of fertilizer solution that you attach to a pipe that you are using for a sprinkler or irrigation. As water flows down the pipe,...
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3answers
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When a microwave oven stops, why are unpopped kernels very hot and popped kernels not hot?

A commonplace empirical observation is that when a microwave oven stops, unpopped kernels are very hot (it's physically painful to touch them) and popped kernels are not. Is there an elementary (or ...
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1answer
64 views

How does a deadcat work?

This is a deadcat. It's a fluffy cover you put on top of a microphone to prevent wind noise on the recording. Lavalier and head-mounted microphones often use pieces of foam over the mic for the same ...
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3answers
95 views

What is the pixel resolution of a human eye?

If it could be possible to build a camera inside a human brain that takes photos of what we see. What would be the resolution of those images in terms of pixel count? This question is not about ...
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Is it an illusion if reheated tea burns my tongue but tastes cold?

I like drinking hot tea or hot water, but I don't like burning my tongue. I believe that certain processes/procedures to prepare the hot tea (or hot water) are more likely to achieve the desired ...
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2answers
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Microwaving versus steaming a Christmas pudding

A slightly belated question on the Christmas theme: a Christmas pudding that you might buy from a supermarket can be reheated by one of two methods: Microwaving for 2 minutes at 900 W. Steaming for ...
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4answers
118 views

What is the explanation of these phenomena? [closed]

A person can jump high raising his 60 kg weight while he barely moves a rock of 60 kg. A person can run fast with his massive 60 kg weight while he barely moves the same rock of 60 kg. An average ...
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3answers
38 views

Difference in weight while pulling weights

Let's say you are using a standard pulley gym machine to lift some amount of weight. If while you exercise you are standing on a weighing scale. What variations in weight if any would occur? Does it ...
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1answer
47 views

How can I turn a floor lamp, that emits light upward, into a reading light? [closed]

How can I turn this floor lamp into a reading light? I want all light exiting upwards from the lamp shade to point down. Do I just buy a mirror and put it on top of the lamp shade? Then the mirror can ...
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2answers
48 views

Attraction between comb and paper bits

It is a common phenomenon that a comb, when rubbed against dry hair, gains electric charge and attracts paper bits. My question is that if the comb induces an opposite electric charge on the nearer ...
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2answers
82 views

Why does porridge start steaming more after the hob is switched off?

I have noticed that when I cook porridge in a saucepan, and stir it with a spatula, it only steams a little bit. But the moment I turn off the (gas) hob underneath, and keep stirring it with a spatula,...
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5answers
70 views

Real life examples comparable to number of electrons in $1\rm C$

In order to teach 7th-grade students of the enormity of the number of electrons in 1 coulomb of charge $$1\ {\rm C} =6.25 \times 10^{18}~ {\rm electrons}$$ I wish to compare this number to a real-...
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0answers
20 views

Does a power station directly control the supplied power or voltage?

The electric grid's "job" is to provide to the end user a steady sinusoidal A/C voltage with an RMS value of 120 V and a frequency of 60 Hz. (That's in the United States - other countries ...
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3answers
73 views

Why can human body sustain relatively high (e.g. up to 30 atm) external pressure?

I found out from the Internet that for average people it's fine to sustain up to 30 atm external pressure, for example when diving. However, given a typical human palm size of 80 cm$^2$, 1 atm means ...
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1answer
51 views

Why does humidity helps keeping heat?

When I turn on the AC to heat my living room, it usually takes a long time, but when I also boil some water in the kitchen(The rooms are connected), the living room heats very quickly. I ran a small ...
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2answers
5k views

How small can a flame get?

Last time I was watching a candle die. After its wick was finished, there remained just a drop of molten wax that was still slowly burning, with a flame that became smaller and smaller, down to a ...
2
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2answers
75 views

Did I make an electric circuit with my cat?

This is definitely the dumbest question I've asked, but I'm curious. My cat was resting her head on my left hand while I pet her with my right. Suddenly, my left hand began receiving regular static ...
4
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2answers
153 views

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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1answer
43 views

Why do titled matchstick burn with higher flame intensity?

When we burn a matchstick when keeping it horizontal, the flame get diffuse very quickly. However, when we bend (lower) the tip of matchstick towards the ground , the intensity of the flame ...
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0answers
76 views

Music coming out of a socket [closed]

This incident happened a couple of years ago, back when I was in school. A classmate and I were sitting in a room when we started hearing music coming out of an electric socket. It took us a while to ...
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4answers
1k views

How does the center of mass move forward on a rocking chair?

When I was rocking on a recliner at home I noticed the combined center of mass of me and the chair would move horizontally (also vertically). The only apparent forces acting on this system is gravity ...

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