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2
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1answer
78 views

How much money can I save on gas by losing weight?

I read somewhere that if you carried around a penny in your car, over the lifetime of the car, you would end up paying an extra penny in gas than if you weren't carrying that penny. I was wondering ...
1
vote
2answers
43 views

Can outgassing produce a significant thrust on a space ship?

There are a variety of materials that outgas in the atmosphere, and I imagine they would do so even more in the vacuum of space. I imagine an object in space would experience a small force as ...
1
vote
2answers
714 views

How easily can the Earth flip?

The recent media attention to sunspot activity (however warranted) reminds me of a question I had long ago. Given the angular momentum and the slight 'wobble' of the earth, and remembering the ...
4
votes
3answers
548 views

Can vinyl LPs store audio above 20kHz and can it be played back? [closed]

If, in the future, humans genetically engineered themselves to be able to hear frequencies significantly above 20kHz (say, up to 100kHz), would they find vinyl LPs a viable method of storing and ...
79
votes
6answers
9k views

Does a gun exert enough gravity on the bullet it fired to stop it?

My question is set in the following situation: You have a completely empty universe without boundaries. In this universe is a single gun which holds one bullet. The gun fires the bullet and the ...
1
vote
2answers
79 views

What temperature is an evaporating cup of water at “room temperature”?

If I put 100 g of water in a cylindrical cup and I know it takes 2 weeks (lets say 1.2 × 106 seconds) at some RH/temp to completely evaporate in my room with a constant temperature, can I ...
0
votes
0answers
53 views

Calculating the theoretical velocity of a projectile

Recently, I made a homemade air powered airsoft gun. I wanted to know how fast it would accelerate out of the barrel, so I tried do do some calculations, but to no avail (keep in mind, I haven't taken ...
1
vote
2answers
81 views

Saturn V horizontally attached to Earth

If the Saturn V rocket were attached to the ground facing in the opposite direction of the Earth's spin, would it in anyway slow the Earth's spin on its axis? How significant of an impact would it ...
5
votes
1answer
228 views

How far away from the Sun does space start to be cold?

I assume that if I stood on the sun, I would be hot. I similarly assume that if I stood about 10 feet from the sun, I would still be hot. However, if I stood in space 93 million miles away, I would be ...
3
votes
1answer
36 views

Sound attenuation when holes size less than wavelength

The actual problem is as follows. There is a gap between a transducer and its circular mounting collar that is about half the wavelength of the incoming sound. What I do not want is for the incoming ...
0
votes
1answer
91 views

Could the Large Hadron Collider accelerate one kilogram of protons at once?

Is it possible to accelerate a very large number of protons in a particle accelerator as opposed to only a few as is regularly done? What's to keep someone from accidentally dumping too many particles ...
11
votes
1answer
2k views

Why don't they use springs as an energy source for cell phones?

I know they used springs for clocks way back in the day and now it's all lithium ion batteries. For reference, consider the Iphone that has a battery with a capacity of 5 Watt hours (18,000 joules). ...
2
votes
1answer
57 views

How much microgravity is there on ISS due to tidal forces? [closed]

I used the equation for the tidal force: $$ F = \frac{2GMd}{r^3} $$ where $M$ is the mass of the Earth ($5.972 \times 10^{24}$ kg), $d$ is half the length of ISS ($50$ m), $r$ distance from center ...
2
votes
0answers
169 views

Could a falling office tower cause the melting of its iron or steel support structure? [closed]

Discussion on META: Questions related to geopolitical events Suppose you have an office tower, weighing around 300,000 metric tons, and has a height of ...
2
votes
2answers
203 views

Vehicle Driving off Cliff (Thelma and Louise movie)

What is the slowest speed at which a vehicle driven off a cliff can clear the cliff without catching its underside between the wheels? In the usual frictionless vacuum, this would appear to depend on ...
3
votes
3answers
746 views

Power to suspend a mass in air

How much power is needed to suspend a mass in the air? The four parts below deal with the same problem. I post them all here, should there be some subtle things I didn't see. The textbook problem A ...
1
vote
2answers
756 views

How much force can bolt cutters exert? [closed]

What's the mechanical advantage of an ordinary, let's say, 3 feet long bolt cutters? How many pounds can they exert? I'm asking because I have a lock which is apparently immune to over 9 tons of ...
2
votes
1answer
109 views

Spacetime curvature effect on chemistry

Do current chemistry / astrophysics / stellar chemistry calculations include the effects of the curvature of spacetime on chemical reactions? For example, the heat transfer from a point closer to the ...
1
vote
1answer
112 views

What is the sum of the angles of a triangle on Earth orbit?

Gauss went out and measured triangles made up of mountain peaks to show that the angles sum up to 180 degree. However, general relativity leads to non-Euclidian space and I would like to get a better ...
6
votes
4answers
2k views

Could we launch a missile from a planet with the mass of Jupiter?

If the Earth had the mass of Jupiter, would we be able to launch a space missile ? Is there a formula to calculate how the launch of 1-Kg payload increases with gravity?
7
votes
2answers
550 views

How many Gs are my clothes experiencing in my washer? [closed]

During a spin cycle I got curious: How many Gs are at play in my simple washing machine? We can assume the drum is 50 cm wide and spins at 1500 rpm.
3
votes
3answers
167 views

What would be the minimum size of a planet which would allow a human being to walk around without falling out in the open space?

On the Earth you can walk - of course we all know it - in the southern hemisphere without falling out in the open space, and you feel no difference between being at the North Pole or on the Equator. ...
1
vote
2answers
87 views

How much fuel do I need to send cubesat 1kg from Earth orbit to Moon orbit? [closed]

How much fuel do I need to send cubesat 1kg from Earth orbit to Moon orbit? And how much stages? For i.e. C12H22O11 + KNO3, polyethylene + oxygen or kerosene + oxygen.
31
votes
5answers
8k views

If the Earth is a good conductor of electricity, why don't people get electrocuted every time they touch the Earth?

Since the Earth is a good conductor of electricity, is it safe to assume that any charge that flows down to the Earth must be redistributed into the Earth in and along all directions? Does this also ...
2
votes
1answer
60 views

If the Moon had a large piece blown out would it remain tidally locked?

I just saw this video on Sonic Adventure 2 trivia where it's mentioned that part of the Moon was blown up but in later games it's whole. It was explained away as the Moon simply rotating to show the ...
0
votes
3answers
95 views

Is it possible to build planet-sized non-spherical structures?

Beyond certain size and density the celestial objects tend to admit a spherical size. I wonder if is there a fundamental mass, density or specific strength related number which when surpassed a ...
0
votes
0answers
32 views

Is it possible that my 750ml water bottle contains spent fuel from a space shuttle launch

Firstly I live in New Zealand which is very distant from USA which is where the space shuttle was originally launched from. So what is the possibility of molecules from the rocket engines spent ...
0
votes
0answers
76 views

How general relativity shows that gravity decreases as we go inside the Earth [duplicate]

Why is it that gravity decreases as we go deeper inside Earth? Can anyone explain theoretically with reference to general relativity?
4
votes
2answers
419 views

Does a clock oscillating in a friction-free hole through the center of a planet run slower than a stationary clock on the surface?

Assume a clock is dropped into a friction-free hole through the center of a symmetric, non-rotating planet, far from any other massive object. Clearly, the clock oscillates from one end of the hole to ...
3
votes
1answer
250 views

How far could the LHC “fire” a proton into space if we (outside LHC) ignore all interactions but gravity?

Very simple question, and frankly quite a silly one, but I'm currently writing a lecture for secondary school kids and I'd love to tell them how far the Large Hadron Collider could fire a proton. The ...
10
votes
2answers
291 views

Would a rocky planet orbiting so close to a very hot star eventually vaporize?

I was thinking about the physics behind a hypothetical scenario where a planet the size and the mass of the Earth is orbiting so close to a very hot star and what the long-term fate of such a planet ...
4
votes
3answers
2k views

Are we increasing the gravity of Earth with our population?

I have these questions related to my question title: Do we, other species and things have our own gravity? How much Gs a human have? Are we effecting Earth, nearby moons and planets with our ...
1
vote
1answer
57 views

Am I experiencing any effect from black holes gravitational pull?

So we know that there is a black hole in the middle of the Milky Way. Am I experiencing any effect from the high gravitational pull of the black hole? If no...then why? If yes...then how much?
0
votes
2answers
77 views

What is a simple calculation to figure out how many watts needed to maintain a hot piece of tungsten?

The specific heat of tungsten is $.13 (\text{kJ /(kg K)})$. 1 cubic cm of tungsten is .0193 kg And the melting point of stainless steel is $1900 \deg \text{K}$ conservatively (giving it plenty of ...
1
vote
1answer
40 views

How much carbon dioxide do we actually ingest from a can of coke?

On this most trustworthy page it states that a 355 mL can of coke contains on average about 2.2 grams of carbon dioxide. As far as I know, this carbon dioxide can exist in solution as carbonic acid, ...
1
vote
1answer
577 views

Continuity equation and pressure head in a tank

Consider a tank which is full of water. We connect a horozontal pipe at its bottom. When the pipe is open, water starts flowing through the pipe, then the velocity of water is proportional to the ...
2
votes
0answers
40 views

SOHO solar observatory, comet numbers and composition

SOHO discovered its 3,000th comet, cementing its standing as the greatest comet finder of all time. Prior to the 1995 launch of the observatory, commonly known as SOHO, only a dozen or so comets ...
0
votes
2answers
77 views

Can a piece of metal have all of its conduction electrons stripped?

Can a piece of metal have all of its conduction electrons stripped? If so, has this been done and for what value?
0
votes
1answer
138 views

What is the potential and kinetic energy of the international space station?

I know it's possible to calculate, but what formulas would I use to be as accurate as possible? I'd like to see how it works for something big and high like that.
19
votes
3answers
5k views

How quickly was the Earth rotating 250 million years ago?

The Earth is slowing at a rate of $4.7\times10^{-4}$ miles per second every 100 years due to tidal forces of the moon. See: http://en.wikipedia.org/wiki/Earth%27s_rotation ...
6
votes
2answers
3k views

How is the Earth heated by a Full Moon?

While the moon is certainly not a good reflector of solar radiation, surely the radiation it reflects back heats the Earth (even if it is a terribly small amount). How would one go about calculating ...
0
votes
2answers
75 views

Do other people's mass count when measuring the attraction of the earth on me? [duplicate]

Suppose that I'm alone on a planet of $M$. From what I learned from school, the gravitation force acting on me is given by $$F=G\frac{mM}{r^2},$$ where $m$ is my mass, $r$ is the distance between me ...
9
votes
3answers
1k views

Is it possible to produce gravitational waves artificially?

Why don't they make a ball with irregularities, say the size of a tennis ball, then spin it very rapidly, so it would produce gravitational waves like a spinning star with irregularities on it? Is ...
17
votes
7answers
3k views

How big are clouds? [closed]

How big are clouds? When I look up into the sky I have no frame of reference, so I don't know if they are 200 feet or 2 miles across. When I am in a plane looking out at a cloud, I try to use the wing ...
37
votes
4answers
4k views

How far out from the Sun is visible light still sufficient to read a book?

Recent pictures from the New Horizons spacecraft, shown below, seem to indicate that, at Pluto's distance, we are entering a twilight zone, with a distinct lack of colors, although that could be due ...
0
votes
4answers
108 views

Does not the mass of those living on the Earth add on to the mass of the Earth or is it too negligible to be cared for?

Source: Earth weighs about 13,170,000,000,000,000,000,000,000 pounds (or 5,974,000,000,000,000,000,000,000 kilograms). Since Earth is too big to be placed on a scale, scientists use mathematics ...
17
votes
2answers
4k views

How big is a 1kW fire?

What is the size/scale of a wood fire that is producing 1kW? I'd like to improve my ability to conceptualize various power scales.
29
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4answers
6k views

How is it possible that the energy needed to stop a train is the same as the (chemical) energy in a pack of chocolate cookies?

Today my friend told me something that blew my mind completely. He said: The energy necessary to stop a train is equal to the energy in a pack of cookies. How is that possible? Is he right? I'm ...
0
votes
0answers
79 views

Can the curvature of space be measured using a swimming pool?

I read somewhere that if the center of mass of two twelve ton elephants was one meter apart then the space they curve would be one nanometer longer. (Though I doubt elephants come that dense) This ...
0
votes
1answer
53 views

Looking at a falling person (vertically) from 60m to the surface, how much wind effect is going to be felt?

I am trying to work out horizontal ranges for a falling person from height (in 10m steps from 0m to 60m). I have used this site http://www.convertalot.com/ballistic_trajectory_calculator.html to ...