# Questions tagged [everyday-life]

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

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### Pulsed Fluid jets

While feeling my shower head, switched to "pulsed jet" mode, exert a higher force on my body as compared to a regular flow jet, I have wondered why a pulsed jet is stronger than a non-pulsed ...
49 views

### Physics of tennis hit

If one takes notice the tennis players hit the ball on the right corner that way: Their last step before the hit is on the right foot, then they hit and then their left foot goes up in the air about ...
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1 vote
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### How best to maintain the temperature of a swim spa?

All the advice I have seen on the internet suggests that it is more economical to keep the thermostat of a hot-tub at its intended temperature, rather than turning down the thermostat when the tub is ...
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### Does the speed of an object underwater change when viewed above?

Let's say a submarine is coming to surface with a velocity $v$ normal to the surface of water and let's say you are the admiral of the navy viewing the submarine from the top. The submarine is exactly ...
1 vote
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### Can we tell anything about the velocity at which a spherical stone falls into a lake based on the sound it makes?

Suppose we have a spherical cow... I mean stone, and we throw it to a lake. Can we tell anything about the velocity (speed and angle) at which it falls based on the sound it makes? And based on a ...
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### Why is it so much harder to keep the same room cool than to keep it warm?

I have read this question: Let me offer a different perspective on this. Cooling is not universally harder than heating. Why is cooling much harder than heating? Now I have noticed that whenever in ...
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### Why is a firm, inflated stand up paddle board at atmospheric?

I have a new inflatable stand-up paddle board, which is supposed to be inflated to 15 psi. I had to pump a long time and it became very rigid—and when I opened the valve it let out a lot of air. I ...
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48 views

### Why are my pavers still wet? [duplicate]

I sprinkled salt on my pavers to stop the weeds growing but now they stay wet a lot longer. I expected the opposite because Adding salt to water makes it boil faster. Adding salt to icy roads melts ...
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### Determine the trajectory of a ball on a golf green that is not level

I want to determine the path of a golf ball when someone "puts" from a location on the "green" to the "hole". The distance between the location of the ball and the target/...
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### Sunscreen protection, SPF, and amount applied: relationship?

In the article How SPF Changes with How Much Sunscreen You Use (last updated Dec 29, 2017), the author says that it is disturbing that insufficient sunscreen (in theory) decreases protection ...
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### Why do we feel cool after switching fan? [duplicate]

Please see that my actual question is not similar to this: Why do we feel cool when we turn our fans on? Suppose I switched my fan on. The air particles start moving. Since, their kinetic energy ...
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1 vote
60 views

### Does electrical wire expand when electricity is flowing? [closed]

My home was recently re wired and after seeing the state of the old wiring I was left wondering why I had to replace the wiring after only 12 years. I know some people will say that I've been had off ...
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1 vote
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### Why does the shape of water flowing down from a squared orifice looks like a chain?

Hello I'm a high school student in Taiwan. My classmate and I are doing a project about the shape of water flowing down from a squared orifice, something like this video. We wanna know is there a ...
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### Why does water collect under a book my laptop is sitting on?

Sometimes I sit in my bed with a blanket over my lap. On top of the blanket I put a hardcover book. On top of the book I will be working on my laptop. So we've got: Laptop Book Blanket My lap ...
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1 vote
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### Warm air syphon to cool down greenhouse

I'm thinking about a very energy efficient way of controlling temperature inside a greenhouse when it's too hot. The goal is to use the syphon effect in order to draw hot air from the top of the ...
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### Why does diffracted light in certain TVs get collimated in six straight or curved rays? [duplicate]

This evening, looking at the television in my apartment, I noticed that the light reflected on it manifested some kind of regular pattern. When the source of light is sufficiently far, this consists ...
32 views

### What causes the lamp above my gas stove to swing like a pendulum when the stove is on?

There is lamp hanging above my gas stove, which when the stove is turned on performs pendulum-like oscillations in an oval trajectory, not unlike the dynamics of Lissajous patterns. The lamp is ...
129 views

### Why did this happen to my pennine?

I went to check on my pasta and found it in a rather odd configuration. (Originally, all the pasta was standing together; the few loose ones there are because I had picked up the pot, semi-drained it,...
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5k views

### If I push someone, what fundamental force do I create?

According to Wikipedia, all forces can be decomposed to four fundamental forces: gravity, electromagnetism, strong interaction and weak interaction. When I push someone, this generates a force. Which ...
• 457
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### Smoke and fluid mechanics

While lighting up a cigarette (I don't encourage smoking) I noticed that the flow of the smoke coming out of it, initially goes in a straight up direction, in a laminar flow, then about 10 cms above, ...
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### Does motorcycle counter-steering work by precessional motion?

When a motorcycle is going over a particular speed ($\approx 20$ m/h or 30 km/h) you learn in motorcycle class the best way to steer is using the so-called "counter steering"; I can't find ...
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5k views

### How do headphones and earphones produce good bass if tiny speakers can't produce low frequency sounds very well?

It's a well known fact that small/tiny speakers cannot produce low frequency sounds very well. Conversely, large speakers cannot produce high frequency sounds very well. Hence the need for tweeters ...
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### Reason of sudden electric shocks? [closed]

A friend of mine regularly gets electric shocks. This happens sometimes when he touches water, his laptop, a chair, metals, people. What may be the reason that he gets electric shocks so often? And ...
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### Why does double edge razor blade not sinks but single edge razor blade sinks in water?

We often see that we can make a double edge razor float on water due to surface tension acting at some angle on all four sides to balance the weight i got this part , but when a single edge razor ...
1 vote
35 views

### Why does my coffee spin the opposite way that I spin the cup?

I was just drinking a latte in a large cup, and when I spun the cup (doing that smooth one handed “mixing” thing that you usually see with a mixed drink or something) I noticed the design on and the ...
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### Why its easier to tie things with multiple loops to the thread for hanging from a pivot? [closed]

We often see that hanging a object by looping a thread around a pivot many times will make the thread to not fall off, but when looped less than critical needed the object falls off, is the friction ...
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### Nature of behaviour shown by tracks of Bike and relation of tracks with length of frame of bike?

If a bike wheels are moving along two paths such that front wheel traces a sinx curve , how to show that back wheel will also transverse a sinusoidal curve with lesser/greater amplitude than the front ...
3k views

### Where does the "water" come from in a mirage?

First, I would like to clarify that I know why a mirage is formed, what I want to know is why is it that when a mirage is formed it appears that a pool of water is present. Like for a palm tree in a ...
82 views

### Why is cup containing coffee hot?

It happened that I was having my coffee and saw this video at the same time. It's an interview given by RP.Feynamn. In that Feynman explains about why is a cup containing coffee hot, he says that as ...
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1k views

### Why is my bluetooth signal able to exit my microwave?

I was shopping for a bluetooth meat thermometer. Since this device would also be used in my combo (conventional and microwave) oven, which is shielded for microwaves, I expected the device to not work....
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### Do all objects we see emit light which then forms an image inside our eye?

Daily life we see so many objects .Often in textbooks the ray diagram for the image formation in eye is shown by showing light rays coming from the object and making an image in inner layer of eye . ...
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### Why at 42° only that the rays has a maximum and then it decreases why intensity pattern is highest at 42°?

As in this stackanswer https://physics.stackexchange.com/a/496453/297949 :"The angle at which the light exits increases, has a maximum, and then decreases again "may someone give a rigorous ...
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### Why we see only one rainbow at some far away and not like many separated by some distance but making that same angle of 42°? [duplicate]

We know that angle needed to see a rainbow assuming sun is at horizon is 42° but then why will that rainbow formation be unique and why not at that angle many rainbows be form in that angle why just a ...
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1 vote
50 views

### Why do we see dark black spots in night sky with the naked eye if those same spots are filled with stars when looked at with a telescope?

When looking in the sky with the naked eye, we often see dark regions with no stars. However, when we look at those same spots with a telescope, it is full of stars or clouds of dust. Why is that?
147 views

### How does the physics of the rotation behaviour of the Roti can be explained?

Many times we see in kitchen when someone makes Roti, they first take the atta (flour) and make a circle shape (not perfect but ideal case let it be) we often see when the roller is moved above it to ...
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### Do electrical appliances reduce the heating bill?

When you use an electrical appliance, most of the electricity used is turned into heat. Will the energy cost of using something like an iron be subtracted from the heating bill making it effectively ...
95 views

### How does a car actually move?

Physics textbooks say that the car's engine spins the wheels which put a force on the ground, which pushes the car (somehow) by Newtons 3rd law. But how does the ground actually make the car move? If ...
88 views

### What is this colored ring effect on my computer screen?

I found rainbows on my computer screen. I can glimpse some faint color if I look at the screen from the side at a sharp angle. It is a lot more obvious when I reflect it off a dark surface (shown here,...
6k views

### At which slope angle is a runner faster than a bicyclist?

On level terrain a bicyclist is faster than a runner. On a steep slope a runner is faster than a bicyclist. (That's why you see bicyclists pushing their bikes uphill.) Can we calculate the angle where ...
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4k views

### Direction of water through a pipe

I was recently asked this following interesting question: How can you find what is the direction of the water flow inside a horizontal pipe, given the pipe is not transparent? You can assume the ...
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236 views

### Why does a heap of sand or a hill have a conical shape?

Sand takes the shape of a cone when it falls on the surface of the earth. Why does sand when poured on the surface of the earth make a conical shape? Why does a heap of sand or a mountain or a hill ...
3k views

### What's the physics behind the jumps with seemingly non-conserved angular momentum?

The #1 rule of sports biomechanics is the conservation of angular momentum. It dictates that whenever an athlete performs an acrobatic jump, the angular momentum that he has created on takeoff is to ...
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### Why does a good thermos keep a cold drink to temp twice as long as a hot drink?

I've owned a number of insulating vessels. It seems the best they can do for keeping a hot drink hot is about 5 hours. The same vessels will keep cold drinks with ice intact overnight, sometimes ...
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### Physics of "Mad Tea Party"

Let's say you have a body rotating about its centre of mass in a rotating frame. But the centre of mass of the body does not coincide with the rotation axis of the rotating frame. We can often see ...
164 views

### Can you superheat coffee?

As far as I know, heating clean water can lead to superheating to over 100 degrees but how clean does it have to be? Coffee is almost all water but is it clean enough to lead to superheating? What ...
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1 vote
49 views

### Percentage of body weight raised for this variation of pull ups?

I have a simple question I think. If one uses one dip bar and do a version of pull ups as follows: what percentage of their body weight is lifted? I.e. how different is it than a regular pull up in a ...
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### What is causing the diffraction pattern on my ceiling?

When I wake up in the morning and look at my curtains, I see a pattern on the ceiling made by the light going through the gap between my curtains. I have added a picture of it below. I remember from ...
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4k views

### What's the heat capacity of pizza?

I'm working on designing a pizza oven. What's a good estimate of the expected heat capacity of a pizza given its radius? A range might be the best way to answer this based on the type of pizza. The ...
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