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

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15
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2answers
189 views

Hourglass on the Moon

Someone asked me this, and I was surprised to find I couldn't answer it: suppose I have an hourglass / egg timer that times two minutes in Earth's gravity. If I used it on the Moon, how long would it ...
3
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2answers
33 views

Why does a cooling car engine crackle?

Why does a cooling car engine crackle? What determines the frequency of the crackles?
10
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6answers
4k views

Can a car steer on a frictionless surface?

Do the front tires of a car act like gyroscopes, such that a car could steer on a frictionless surface?
3
votes
1answer
142 views

Can you safely draw sparks from the nose of an electrified boy?

From Purcell's Electricity and Magnetism A spectacular conclusion of one of the popular exhibitions of the time was likely to be the electrification of a boy suspended by many silk threads ...
-3
votes
0answers
35 views

Why does hot food give off vapor?

Does your food melt and then boil to give off this gas? What is the vapor here?
0
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1answer
36 views

Why do car wheels seem to roll backwards [duplicate]

For many years i have been wondering about this. When a car stars moving the wheels seem to work normally but as the car speeds up, the wheels seem to roll backwards. Of course that does not happen in ...
9
votes
3answers
2k views

How can rising bubbles shrink and disappear?

I was recently looking at a Wurlitzer juke box, and noticed something strange. It's decorated with liquid-filled tubes. Gas bubbles are injected at the bottoms of the tubes, and the bubbles naturally ...
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 ...
1
vote
0answers
20 views

Is there any advantage to using simple syrup over just dissolving sugar and waiting a minute?

When making coffee, I want to sweeten it with sugar. Many coffee shops offer simple syrup which is essentially just a solution of water saturated with sugar. Obviously, this has the advantage that ...
5
votes
2answers
1k views

Hit a bottle of beer on the top with another causes the first to spit all the gas, why?

So, on the other day me and my colleges were discussing the following phenomena: Pick two open bottles of beer. With the bottom of the first, hit the second on the bottleneck, in the following way: ...
42
votes
4answers
4k views

Why wet is dark?

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 ...
2
votes
2answers
288 views

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?
6
votes
3answers
633 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?
7
votes
4answers
10k views

Why is there water coming out of a car’s tail pipe?

I notice yesterday that my neighbor’s car had water coming out of the exhaust pipe in the morning. My first response was since the hot exhaust is hotter than the cold tail pipe, heat is transferred ...
13
votes
5answers
12k views

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 ...
3
votes
0answers
279 views

If human eyes watch an area, what will be shape of its capturing shape? rectangle? half spherical? [migrated]

A normal camera can capture a rectangle shape image. If human eyes watch an area, what will be shape of the captured region? Rectangular? Half-spherical?
1
vote
2answers
82 views

What's Optimal About Six Legs According to Physical Laws? [closed]

In many respects the insects can be regarded as the most successful class of animals in evolutionary terms. And one of the most common features of insects is that they (mostly) all have six legs. Not ...
2
votes
2answers
95 views

Order of magnitude estimation for some intriguing questions

The physics TA showed us a few examples in which one can estimate many things from first principles, sound logic, and scaling arguments. This led usually to understanding of why some numbers have the ...
0
votes
4answers
231 views

Does the pressure inside a tire equal to its average ground pressure?

On one hand, I think they should be equal since the external force and internal force are equal in equilibrium. On the other hand, I don't see anything related between them, the inside pressure is ...
20
votes
5answers
4k views

Why are a motorcycle's front brakes more effective than back?

I've noticed that when I apply the front brakes on my bike it stops quite quickly. If I apply the back brakes at the same speed, it skids rather than stopping quickly. Why?
22
votes
8answers
4k views

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, ...
3
votes
3answers
44 views

Why is the required tire pressure inversely proportional to the volume/size of the tire?

I once noticed a tire pressure table on a farm recommended a tire pressure of around 1.0 bar (I don't remember the exact number, but it was definitely below 1.9) for the rear tire of farm tractors. ...
0
votes
0answers
14 views

How does the Triboelectric effect work? [duplicate]

The general description for the Triboelectric effect (the main cause of static electricity in everyday life) is that when two certain materials come into contact, electrons are transferred between ...
3
votes
4answers
117 views

Why Does Angular Velocity Increase as Radius Decrease?

Suppose a child were to ask you why a tetherball (picture below) seems to speed up as it wraps around the pole. How would you explain this to them? Certainly you wouldn't say something like, "Angular ...
2
votes
5answers
415 views

Dying question: Tractor wheels — large vs small

This question has stumped me for over a month now: Why is it that a tractor has large wheels at the back and small wheels in the front? Current ideas: small wheel in front --> lower center of ...
9
votes
4answers
3k views

Why does a ball bounce lower?

If a ball hits the floor after an acceleration then why does it bounces lower? I mean the Energy is passed to the floor then why does the floor give back less Energy?
19
votes
5answers
2k views

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 ...
12
votes
2answers
205 views

Why is cooling much harder than heating?

I'm trying to invent a distillation apparatus that runs solely on electricity. Suddenly, I realized that cooling things is really hard, while heating them up is so easy. Actually, it seems that there ...
2
votes
1answer
86 views

Is it possible that a battery goes flat faster in a cold environment?

I own an old iPod Classic with original lithium-ion polymer battery and I use it primarily while running. Recently I discovered that when a temperature outside is low, usually below 5 C degrees, the ...
3
votes
2answers
318 views

How do I figure out the momentum of a water balloon when it reaches the person I am throwing it at?

Recently an experiment was performed in which myself and a partner filled a water balloon and threw it back and forth at each other without breaking it. We gradually increased the distance at which it ...
12
votes
1answer
88 views

Why does water appear still near the shore

Often when there's a light wind I notice this behaviour on lakes that there appears to be a very distinct line between the water with waves and the calm water. I don't know how well it comes through ...
11
votes
1answer
73 views

Why does my jam often “fall up”?

I often get my jam out of the refrigerator, and it looks like this: That is, all the jam has gone to the top, looking as if the jar has been sitting upside down. However, this happens fairly ...
10
votes
2answers
379 views

a weird image of sun

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 ...
2
votes
1answer
48 views

Why is a bow always arch-shaped and not of other shape?

Everytime I see a bow , one thing is greatly noticable- its arch shape. I have never seen bow other than this shape. But what is the cause for taking this shape for the bow? What is the physics behind ...
8
votes
2answers
866 views

How does varying temperature affect the accuracy of grandma's pendulum clock?

I have an antique pendulum clock(my granny's!) . If I detail it, This clock is approximately 5 feet tall and enclosed by wood and below it its glorious pendulum oscillates . It gave more or less ...
7
votes
1answer
265 views

Where is the “event horizon” on a basketball hoop?

I'm watching a lot of basketball this month. A common event is the ball going part way into the hoop and then coming out again. Announcers sometimes claim that the ball was "halfway through" when it ...
3
votes
1answer
20 views

Can physicist estimate is it safe to walk/drive on ice? [closed]

I'm curious about the following: Suppose that I know the the weather forecasts of a given place. How can I compute from that data whether or not it is secure to walk or drive by a car to an island.
2
votes
2answers
89 views

Kitchen floor dries faster with lights on?

My mother used to leave the lights on in the kitchen after washing the floor, saying that it would dry faster. Does this really happen, or is it just a superstition? If true, how substantial is the ...
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 ...
8
votes
1answer
264 views

Why does my body create interference with my clock radio while in bed?

I typically listen to NPR in the morning from a clock radio next to my bed. There are days when just moving my body, even my arm or leg, is enough to cause interference with the radio to dramatically ...
2
votes
1answer
87 views

Why is shifter necessary in cars? [closed]

Electric cars do not have shifter, while gasoline cars do (manual or automatic, it doesn't matter). Why?
0
votes
1answer
21 views

Most efficient way to cool a two story house with two fans?

Suppose I have two fans in my two story house, one in an upstairs window and another in a downstairs window. I want to cool my whole house; it is cooler outside than inside. Is it more efficient for ...
1
vote
0answers
24 views

How different sizes of water bubbles behaves in space

I watched a YouTube video of Chris Hadfield talking about different preventive measure for spills in space station. He is using water to demonstrate spills in space station. At 0.24sec the initially ...
1
vote
1answer
62 views

Can one calculate the distance from Earth to the camera, given a single picture?

Given an image of (part of) a sphere of known size, can one calculate the distance to the camera based on the relative size of the sphere in the image? My instinct is "no" unless you have some fixed ...
2
votes
1answer
271 views

what kind of wings would a person need to fly?

I heard from a teacher in school that in order to fly, he would need a wingspan much wider than the wood shop where he was standing. Thinking back on it, I assume the number of times you can beat your ...
23
votes
3answers
4k views

Is this really a golden ratio spiral?

In this blog post, I found this picture: Does the water really form golden ratio spiral in such cases? Or is the photo just a provocative example, without physics grounds for claims about ...
1
vote
2answers
112 views

Add weight in front or behind the moving wheel?

Consider a wheel with bearing and axle bar rolling on level ground. If I want to help the wheel continue moving longer(or faster speed), should I add weight by moving the rider body in front or ...
5
votes
3answers
561 views

Benefits of rear spoiler in cars

What would be the benefits of rear spoilers in cars, like this one:
3
votes
2answers
97 views

Why can't we reach the ends of rainbow?

Rainbows are spectacular things. But I imagine why we can't reach to the ends of rainbows. Do rainbows have no ends ? If so, why can't we reach at them? If you go closer,they will go further. Why?
2
votes
2answers
78 views

What make us fall when we move on ice? [duplicate]

This is a common phenomenon and most of the people have encountered this while moving on ice:falling down! Why does this occur? According to me, it is due to lack of static friction. But why will it ...