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

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18
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2answers
810 views

How hot does the tip of a pencil get while writing?

When writing with a pencil, there seems to be quite a lot of friction - which seems like it would induce heat. How hot would the tip of a #2 pencil get writing on normal copy paper?
7
votes
1answer
1k views

How does the boiling time depend on the number of eggs

My nephew showed me an exercise from his school-textbook about boiling eggs. Here is the exercise (translated from german): To make one hard-boiled egg in a pot of water one has to put it for 8 ...
13
votes
2answers
2k views

How does a sponge “suck” up water against gravity?

If I take a sponge and place it in a shallow dish of water (i.e. water level is lower than height of sponge), it absorbs water until the sponge is wet, including a portion of the sponge above the ...
4
votes
2answers
139 views

Cycling down a mountain

I am Dutch, so I cycle a lot, hence the following question. Say I am standing at the top of a mountain on my bicycle. I have an amount of energy $E$ available. Say that after the slope of the mountain ...
2
votes
2answers
115 views

Harmlessness of a pure alpha decay particle

From my high school physics class I remember that there are some particles which exhibit pure alpha decay (i.e. alpha decay to there stable isotope), like Po-210, Po-211 and Bi-209. What I also know ...
-2
votes
1answer
86 views

How does the formaldehyde leak into the food from bamboo cutting board? [closed]

http://food.thefuntimesguide.com/2010/07/bamboo_cutting_board.php Some bamboo cutting boards are glued together with adhesives that have formaldehyde in them — which could eventually leak into and ...
2
votes
3answers
232 views

Can random constructive interference with sound waves cause damage?

Any two sound waves have a random chance to constructively interfere with each other at a given spot and this will cause an increase or decrease in pressure. So is it possible that a large number of ...
6
votes
1answer
337 views

The quickest 6-3 play in baseball: to bounce or not to bounce?

What's the quickest way the get the ball (say from shortstop) into the first-baseman's glove, given some fixed initial (throwing) speed? Directly or with one bounce? I'm fairly sure that the answer ...
11
votes
2answers
1k views

Is the meander ratio of a river $= \pi$?

To get from point $A$ to $B$, a river will take a path that is $\pi$ times longer than as the crow flies (I think this result is from Einstein). What is the proof of this, and how well does it hold ...
0
votes
0answers
56 views

Color of sky scattering by sky dust [duplicate]

Why does we see sky like blue in maximum time? We know violet has less wavelength, so we should see sky like violet. My assumption is that, violet is not primary color and not sufficient in the ...
1
vote
1answer
1k views

Calculate the distance between two points from iPhone Camera

I want to calculate the distance between two objects using an iPhone camera. Suppose I'm standing with my iPhone 10 feet away from the objects. Now, I want to calculate the distance between those ...
38
votes
16answers
4k views

Quantum mechanics and everyday nature

Is there a phenomenon visible to the naked eye that requires quantum mechanics to be satisfactorily explained? I am looking for a sort of quantic Newtonian apple.
5
votes
1answer
381 views

Physics of every-day life: rotating bag of tea

Whilst studying for my physics courses, I like to drink tea. Today, I noticed that if you pull a bag of tea out of a hot cup of water, it gradually starts to rotate, picking up speed as time ...
4
votes
1answer
181 views

What is the minimum pressure difference for your ears to pop?

I'm assuming the answer to this largely varies from person to person. Assuming you could instantly change the pressure around your head by amount $\Delta p$, what is the minimum $\Delta p$ for your ...
21
votes
7answers
5k views

Why Won't a Tight Cable Ever Be Fully Straight?

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 ...
9
votes
2answers
1k views

How does my hand amplify an FM radio signal?

I have a gizmo that broadcasts an FM radio signal from my phone's headphone socket to my car's radio antenna. Sometimes, there's another station on the same frequency with a stronger signal and my ...
4
votes
3answers
10k views

Why don't electric workers get electrocuted when only touching one wire? [duplicate]

I know that when electricians work on the poles on the streets, if they only touch one wire at a time they will be fine. However, from my understanding, the negative wire is connected to a large ...
0
votes
2answers
6k views

Does more reflective aluminum foil make a room cooler compared to less reflective foil?

Aluminum foil is said to be not absorbing light at all. It reflects light. So, does it mean that a more shiny aluminum foil will reflect more light and thus make the room more cooler as compared to ...
14
votes
1answer
301 views

Modelling the movement and jumps of a chalk while drawing a dashed line on a blackboard

You probably know that if you try to draw a line using a piece of chalk on a blackboard , under some conditions (for example, $\alpha<\frac{\pi}{2}$ in the picture below) you will have a dashed ...
1
vote
1answer
79 views

Why do lumps of sugar break more easily when blowing in it?

My question is simple, when you have a small lump of sugar, it's hard to break it with your bare hands, but when you blow in it, it appears to be more easy. (it's a piece of advice i learned for my ...
25
votes
6answers
7k views

How do whisky stones keep your drink cold?

From a discussion in the DMZ (security stack exchange's chat room - a place where food and drink are important topics) we began to question the difference between how ice and whisky stones work to ...
6
votes
1answer
698 views

Why is it hard to breathe when cycling against the wind?

Sometimes when I bicycle against hard wind, I find it difficult to breathe. Others I have discussed it with have also noticed this effect. A possible related phenomenon that I heard from an ...
2
votes
0answers
69 views

Seashell occurrance

Sometimes, sea shells accumulate on the sea shore, but sometimes they will instead be dragged back out to sea. What are the main physical factors that determine which of these things will happen?
3
votes
1answer
212 views

Does tapping at the side of a bottle prevent shaken soda from bubbling over?

Anecdotal evidence has it that a bottle of soda that was heavily shaken will not bubble over if tapped at the side multiple times. Yet I wonder: Has the tapping really any effect? Or could it be that ...
4
votes
3answers
475 views

Does more rain strike a vehicle while moving or while stopped (or neither)? [duplicate]

Assume there is a rainstorm, and the rain falling over the entire subject area is perfectly, uniformly distributed. Now assume there are two identical cars in this area. One is standing still, and ...
16
votes
7answers
8k views

Does an empty refrigerator require more power to stay cold than a full one?

Given that everything else is equal (model of fridge, temperature settings, external temperature, altitude), over a given duration of having the door closed, does it require more electricity to cool ...
3
votes
4answers
217 views

Would a phone move upon vibration in a completely uniform situation?

I was sitting down yesterday and saw my phone vibrate on a side, and it moved about a centimetre per vibration. I wondered why it moves, and thought perhaps that the side it was on had a slight ...
6
votes
3answers
310 views

How can I determine the coefficient $k$ in $ \dfrac{dT}{dt} = -k(T - 100 \mathrm{^\circ C}) $?

I recently spend some time on cooking and I'm curious about the time evolution of the temperature of the water. I did some experiment and the temperature is of the form $$ T = 100 \mathrm{^\circ C} + ...
9
votes
3answers
745 views

How hot is the water in the pot?

Question: How hot is the water in the pot? More precisely speaking, how can I get a temperature of the water as a function of time a priori? Background & My attempt: Recently I started spend ...
8
votes
1answer
595 views

What determines bubble locations in boiling water?

Something a little different to our usual fare. I was boiling a pan of water for cookery the other day, and got to wondering what caused the location of the bubble streams from the bottom of the pan. ...
1
vote
1answer
75 views

Reducing deposition on power supply wires

From my house there are two wires, i.e. a live and a ground wire which are placed on the power supply lines by a hook. They are not tightly jointed because of some reasons. These two wires are also in ...
10
votes
5answers
32k 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 ...
6
votes
5answers
6k 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 ...
2
votes
2answers
376 views

Why does tea rises in the pot but water don't?

I was wondering when I boil water in a pot it only shakes too much while boiling. But I could not figure out why tea rises in the pot when we boil it. it is also a liquid but it starts rising up till ...
1
vote
2answers
587 views

What will happen if we place salt water on a induction cooker?

As we know that induction cooker works on the principal of induction of current in a conducting plate. So I just wanted to know what will happen if we place salt water in a plastic container on the ...
5
votes
1answer
173 views

What pressure or tension occurs in a glass jar when I pour boiling water inside?

Sometimes it happens that when you pour a boiling water into a glass jar, it cracks. Since glass is very hard material and resilient to pressure, the tension must be very high. Is it possible to ...
10
votes
2answers
314 views

What if the lid of a pressure cooker was suddenly released?

My dad and I have tried to calculate the strength of the explosion if the lid was suddenly freed. We took some measures: Lid mass: $0.7 \textrm{kg}$ Lid surface: $0.415 \textrm{m}^2$ Internal ...
17
votes
2answers
404 views

Stripeless cleaning of windows

Cross post: http://chemistry.stackexchange.com/q/4377/22 Last week I was discussing with a friend how we thought the stripeless cleaning of windows is achieved when using a cleaner like Windex ...
5
votes
4answers
340 views

Can a balloon be used as an anchor point for a pulley?

For a physics/ engineering contest, I want to use a large balloon as an anchor point for a pulley. This would allow me to raise and drop masses. However, in testing, when I pull on the pulley the ...
2
votes
3answers
203 views

Flushing water-Is it related to Coriolis force? [duplicate]

There are videos and articles on the internet which demonstrate that water flows down a flush clockwise in Northern Hemisphere and anti-clockwise in Southern Hemisphere. Here are a couple of links ...
4
votes
3answers
3k views

Using Electrostatic Force to Repel Dust From an Object

I have two 4,000V, 2.5mA, DC power supplies and am attempting to use them in such a way to cause a 6x4x1-inch ABS plastic object to repel dust from the ambient air and prevent this dust from settling ...
3
votes
1answer
130 views

What's the principle used in infant breath monitor devices?

Such a device consists of a sensor pad that is placed under a mattress: What's the principle it uses to detect breathing?
1
vote
1answer
86 views

What controls the heating ability of steamers?

Pictured below is a standalone steamer used for foaming and heating milk for milk-based coffee drinks like cappuccinos and lattes. They can be filled with water up to the pressure relief incorporated ...
19
votes
11answers
3k views

Are there still 'everyday' phenomena unexplained by Physics? [closed]

There are two very famous quotes from German Nobel Laureate Albert Abraham Michelson that are remembered mainly for being extremely wrong (especially since he said them just before two major ...
1
vote
1answer
390 views

Is my electric power cord creating magnetic field when coiled?

Simple question. But I was wondering, does my mac power cord create a magnetic field when its all coiled?
33
votes
4answers
10k views

What causes ballpoint pens to write intermittently?

After a while, a ball point pen doesn't write very well anymore. It will write for a little distance, then leave a gap, then maybe write in little streaks, then maybe write properly again. It seems ...
7
votes
5answers
2k views

When driving uphill why can't I reach a velocity that I would have been able to maintain if I started with it?

Consider these two situations when driving on a long straight road uphill: Starting at a high velocity $v_h$, which the car is able to maintain. Starting at a lower velocity $v_l$, and then trying ...
4
votes
1answer
283 views

why do lightbulbs sometimes unscrew by themselves?

I've seen some light fixtures which exhibit the behavior of lightbulbs gradually unscrewing by themselves.
10
votes
3answers
3k views

Does sound propagate further in freezing weather?

A few days ago I went for a walk in the evening. We're having winter with a little snow and freezing temperatures. We're in a quiet, shallow valley with a train station about 1km from us. I heard a ...
1
vote
1answer
587 views

Confused about fire?

Im confused about fire. The way I see it : Heat creates (kinetic) energy in mass and this creates stronger vibrations of atoms. When those vibrations are strong enough the electrons interact ...