Questions tagged [estimation]

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2answers
35 views

At what speed does air drag becomes important?

Imagine an object that wants to move at a speed $v$ trough a fluid. I was thinking that when i ride a bike, there is generally a speed at which air drag becomes a problem, but if i ride slow i does ...
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2answers
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The Leaning Tower of Pisa [closed]

Can we calculate the time when the Tower will lean to the extreme point that its center of mass will be out of its balance...?
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1answer
91 views

What would happen if a miniature black hole (or a PBH) would pass through Earth at relativistic speed?

There are a lot of questions about a small BH and the Earth, none of these answer my question specifically. And there are contradictory answers. Some of them state that the effects would be negligible,...
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6answers
3k views

If the moon became a black hole, how much would it eat in a day?

I have been thinking about the moon becoming a black hole. I was thinking about how much it would eat a day. How much mass would it suck in in 24 hours on average? I am writing a story where the moon ...
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0answers
24 views

What would happen if two gas giants colliding?

If two rocky planets collided each other then there will be lot of heat and explosion. But what will happen if two gas planets collied each other (Jupiter and Saturn)? Will it cause the explosion or ...
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1answer
42 views

How can you model how far a spinning cylinder will move forward during free fall?

I am a high school student and have just started calculus. Part of my project involves doing this experiment where I drop a cylinder from about 10m high with a large backspin and see how far forwards ...
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3answers
73 views

How much energy is required to boil and maintain boiling water temperature for a set time period?

I am trying to calculate the amount of energy required to bring 1 litre of water up to boil (from 20 degrees C to 100 degrees C) and to maintain the water temperature at 100 degrees C for a period of ...
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2answers
80 views

What would happen to the Sun if you reflect all its emitted e.m. radiation back? [duplicate]

What would happen to the Sun if you would reflect, in whatever way, all the outgoing electromagnetic radiation (Solar winds can be neglected)?
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1answer
151 views

Could a human, even in principle, hear a gravitational wave? If so, how powerful must it be? [duplicate]

Sufficiently powerful gravitational waves can excite an eardrum and be heard. How powerful would the waves have to be for a human to actually hear them, and what would be the side-effects of that ...
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0answers
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How much does $g$ vary according to the position of the moon?

The gravity of the earth or more specifically the gravitational acceleration, $g$, is the acceleration objects with mass experience toward the earth due to gravity. How much does this vary according ...
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1answer
43 views

What if static electromagnetic field is turned off? (in vacuum)

Lets assume that there is static electromagnetic field that has $E=17mc^2$ and $p=8mc$. At some time $t=t_0$, the field is turned off. (e.g. the electric current of coil went to zero by resistance, ...
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2answers
98 views

How long would it take for something really far away, say $300,000,000 \ \text{meters}$, to feel the force from a pull of a rope attached to it?

My friend phrased the original question like this: If I tied a rope to myself and wrapped it all the way around the earth and then pulled (assuming the rope was already taut), which direction would I ...
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0answers
91 views

Gravitational waves emitted by accelerating rocket

What is the gravitational wave luminosity of a rocket with mass $m$ (kg) accelerating at $\Delta v$ (m/s$^2$)? Intuitively, I expect the luminosity (in Watt) to depend on the mass and acceleration. ...
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0answers
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How large would and asteroid need to be to cause damaging earthquakes?

Reading this acticle www.mirror.co.uk/news/weird-news/huge-asteroid-could-cause-earthquakes-7019482 I was surprised at the claim that a 2.4km wide asteroid could cause earthquakes on earth by way of a ...
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4answers
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Could I survive at (or near) absolute zero with a very, very, very thick sweater?

Imagine I'm in an infinitely large vacuum and have a special apparatus built into my body that allows me to breath, eat, pee/poo, etc. and never age. The vacuum is similar to deep space and has no ...
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1answer
79 views

How does $g$-force relate to time dilation?

In the imdb.com goofs page of the movie Interstellar, I found this statement: How does time dilation affect $g$-force? If this could be explained in Laymen's terms it would be much appreciated.
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1answer
43 views

If Moon escapes to infinite distance from Earth gravity, will its gravity change?

As we know that gravity of earth influences Moon gravity and vice-versa. Suppose, Moon escapes to infinite distance where there is no other object to affect it, will we weight higher there? If yes how ...
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2answers
120 views

Calculating actual resistance in plank rowing

I hope this is the correct TA here, but please consider the below rudimentary diagram, which depicts bodyweight plank rows using a particular device. The image shows the setup of the device, and ...
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2answers
168 views

Open window in hot room, how fast will temperature equalize? [closed]

I am currently sitting in a warm room. I just opened a window to the outdoors, where it is cooler. Middle school science says the warm air should move toward the cool air, which should (in theory) ...
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1answer
44 views

Is there really a southwards 1 N force on me due to my latitude?

I live in the UK at approx. $53 ^\circ$ latitude. The horizontal component of my centripetal acceleration due to the Earths spin works out at $1.3$ N. That's like the weight of an apple. Is that ...
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1answer
409 views

Does Earth's Gravitational pull increase with time?

Gravitational field depends on mass ($g = \frac{GM}{r^2}$) and every year many outside cosmic objects like asteroids or tiny object are hitting earth. So I think may be in a very microscopic amount ...
2
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1answer
30 views

Quantum vs Classical estimation using Fisher Information

Is it possible to have a different estimated value of a parameter by Classical Fisher Information (CFI) compared to Quantum Fisher Information (QFI)? Say, for example, I am plotting, $\mathcal{F_{\...
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1answer
25 views

How close would a supernova be to endanger the astronauts on the ISS?

How close would a supernova be to endanger the astronauts on the ISS? Would Betelgeuse be close enough?
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3answers
99 views

Why aren't rockets launched in movement? [closed]

Rockets launched to reach orbit usually start from a stationary position, engines are started and the rocket slowly gain acceleration upwards, eventually reaching orbit. What I'm thinking is that the ...
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1answer
42 views

Could one, with enough electricity to spare, use particle accelerators to mass produce heavy elements

If electrical, and economic limitations are ignored, would it be possible for a civilization to mass produce many millions of tonnes of useful heavy elements using particle accelerators? Could they ...
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3answers
134 views

Please clarify Uranium-235 critical mass achievement and how much energy is released

I've been watching an MIT course which explains the way that a nuclear bomb works. I am not a physicist or physics student, however; I am a computer scientist. As such, I am not looking for a level of ...
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1answer
49 views

Quantum Fisher Information vs Classical Fisher Information

I am currently studying about Fisher Information and have a rather simple doubt which I can't figure out. Is it possible to have Quantum Fisher Information (QFI) more than Classical Fisher ...
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2answers
73 views

Why can you in physics exercises neglect the effect of air drag in case of basketball but not in the case of ping pong ball?

This is not a homework question or anything. I have finished schools and I always wondered why in physics exercises you can neglect the effect of air drag for example in case of basketball and I haven'...
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5answers
12k views

Why isn’t CERN afraid of a fusion reaction in the LHC?

Given that they can reach terrifying energies and temperatures, why isn’t fusion of protons a concern? After all, they start with a plasma and ram protons into each other. At some point the strong ...
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1answer
28 views

Estimate height of atmosphere [closed]

Working on a estimation problem and we've been asked to estimate the height of the Earth's atmosphere given its mass is $10^{19}\mathrm{kg}$ and we must assume the density is $1\mathrm{\frac{{kg}}{m^3}...
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2answers
55 views

Theoretical value of electric dipole moment of a molecule

Consider a hydrogen chloride molecule (HCl). Let's assume that we're given the distance between hydrogen and chlorine nuclei $d=1.27 \times 10^{-30} \mbox{m}$. How to calculate electric dipole moment $...
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1answer
24 views

How we calculate potential energy in best accuracy?

This question may be a bit ridiciolus but let me explain. I'm not talking about the formula, I am talking about, what is the best accuracy of calculating the potential energy. For example, let I ...
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1answer
95 views

How high can you jump (at the corner) on Cube-Earth?

I have read this question: Is the force of gravity always directed towards the center of mass? And G. Smith's answer lists a site where they specifically talk about this case mathematically. https:/...
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Rpm vs Electrical Output | Relationship

Is there a mathematical law for when you spin an electric generator a certain amount of times faster you can figure out how many times more electricity is produced?
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0answers
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In parameter estimation, how does one obtain an estimator?

To estimate the value of a parameter $\theta$, we require an estimator $\hat{\Theta}(\epsilon)$, the estimator associates a particular measurement value $\epsilon$ with an estimate of the parameter $\...
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3answers
301 views

Why viruses cannot be seen?

With the coronavirus pandemic, a lot of websites are publishing articles about viruses. In particular, I've seen some of these stating that viruses cannot be seen because they are so tiny they cannot ...
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1answer
31 views

What will be the absolute gravity of Io moon if Jupiter's gravity not in effect? Can GR explain it?

It is noted that the distance between Io moon to Jupiter planet and our Moon to Earth is nearly same. However, the ratio of gravity Earth/Moon is 80.4 times vs ratio of gravity Jupiter/Io is 20276.7. ...
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1answer
53 views

What will be the mass of the sun when the core is depleted of hydrogen about 5 billion years from now?

Our sun converts 600 million tons of H to He every second, that is 5 million tons of matter into energy through nuclear fission. However, as the core of the sun continues to shrink the outer layers of ...
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1answer
29 views

Water physics for continuous fall

I would like to know if there is a standard formula to calculate how much volume of water is needed per area unit in order to get a continuous/uninterrupted water flow. What I would like to achieve ...
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1answer
49 views

Question about a theoretical bee's power to lift

Given a theoretical bee with sufficient (not limited) wing power and material strength of the wing, but with realistic dimensions is it possible for it to lift a human? If not, what are the ...
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1answer
36 views

Acceleration of human accelerated into vacuum

How would one calculate the acceleration of an object released into a vacuum? Imagining you have a Person in an airlock and that airlock suddenly opens depressurizing instantly from 1atm to 0 how ...
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5answers
4k views

Do planets orbiting stars emit gravitational waves?

I have heard it said that charged planets could not orbit a massless (low mass) oppositely-charged star based on electromagnetic attraction the same way they can with gravitational attraction, because ...
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1answer
69 views

Could a Dyson Sphere-like object be made to encase a black hole without collapsing?

In this question, I'm not asking about the feasibility of building a black hole Dyson Sphere or the effectiveness, I simply want to know if an object could stay in a locked position encasing a black ...
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1answer
38 views

Discerning binary stars

What is the minimum magnification that one would need to discern a pair of binary stars if viewed from Earth? Are there factors other than magnification that matter? If so, why?
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0answers
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Air drag on moving air

Assuming we have a $0.6\ \mathrm m$ diameter fan blowing $3\ \mathrm{m/s}$ as measured by an anemometer at the exact exit of the fan (it was actually measured at the entrance), what is the speed of ...
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1answer
218 views

How long would it take to get to the Hyperion proto-supercluster?

Right now, we set a ship carrying no humans going to the Hyperion supercluster (redshift is $z=2.45$, so around $11$ billion light years from Earth) at a velocity of $c/2$ ($c$ being the speed of ...
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7answers
15k views

Why is it apparently not dangerous to fire a shotgun (such as when “skeet shooting”) into the air?

If you fire a gun or rifle into the air, whether straight up or at an angle, as I understand physics, a metal projectile will gain surprising momentum on its way down again, more than capable of ...
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0answers
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How do you estimate the accretion rate onto a black hole (or neutron star)?

Assume we have a heavy mass like black hole and there is an accretion disk around it. At a black hole (eg. pics of the bh. of m87) some parts of the given disk glows brighter than the others. How can ...
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1answer
95 views

How to understand Newton's law of universal gravitation?

Hi I am a high school physics student and I am currently struggling to grasp the concept of Newton's law of universal gravitation. I am really confused with how this works. So do all objects attract ...
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0answers
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What is the actual entropy of the Universe [closed]

I know that it depends on scale, but for example, for an experimenting coissing a coin, What was the maximum run, 20 , 30, that doesn´t influiate taking account that the velociy of the information is ...

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