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Questions tagged [estimation]

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77 views

Force required to propel mass in vacuum [closed]

I'm not mathematically inclined. At. All. I'm a massage therapist and mental health provider. I am, however, writing a book that takes place in space. My main character (MC) is 4'11" and weighs 95#/~...
0
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0answers
59 views

At what speed in air would a solid object turn to plasma?

Just curious, friction can heat up what ever is moving. The faster something moves the quicker it heats up. Is it possible in the perfect scenario to turn a speeding solid object to plasma through ...
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0answers
37 views

What happens with the energy released after a particles collision?

From the website of CERN: "Collisions in the LHC generate temperatures more than 100,000 times hotter than the centre of the Sun.". My question is, what happens to the energy released after the ...
2
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1answer
56 views

Schwarzschild Radius of the Universe Part 2 [duplicate]

There seems to be some confusion as to what I am asking, so I am editing this for clarity. I know the universe is not a black hole. But if I could take all of the matter, (seen and unseen including ...
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1answer
64 views

How much more precise would LIGO have to be?

The planets and a spinning black hole both drag their local frames and thus generate gravitational waves The amplitude should be proportional to the size of the celestial body, while the frequency of ...
-1
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1answer
28 views

Why is it dangerous to approach an unearthed WW2 100kg aviation bomb? [closed]

When some unexploded 100kg bomb from WW2 is unearthed, there is advice for people not to approach it. Or sometimes it is said that the bomb needs to be detonated in the place where it was found ...
0
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1answer
41 views

How does quantum tunneling work in a bigger mass?

im trying to figure out the probability of a 9 y/o kid going right through an object. im trying to do this with a compacted form of schrodingers equation: e^(-2*(m*v/H/2pi)*l) where l = 22,34mm, h = ...
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1answer
39 views

What fraction of events goes through a small area $dA$ a distance $r$ from a spherically symmetric point source as $r\to 0$?

I'm not sure how to use limiting principle to estimate the N fraction when r -> 0 and small area dA stays fixed $ \lim N_{r\to\infty} = \lim\delta A/(4\pi r^2)_{r\to\infty}$ = 1/2 N ? How?
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2answers
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Why do people not have gravitational attraction? [closed]

Gravitational theory says every thing that has mass attract each other. So why don't people attract each other and overlap
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2answers
40 views

How much will a hole in the wing of a bumblebee affect its flying? [closed]

let's assume the holes are round shape in the middle of both wings. if the size is 1% of the whole wing, how much will be the impact? i assume this is not linear, how much will be affected if the hole ...
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3answers
3k views

Would a galaxy be visible from outside, but nearby?

We all know the typical sci-fi image of a guy standing on the ship deck and able to see a full galaxy. If you somehow were able to stand a few lightyears away from a galaxy would you be able to see it ...
3
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2answers
41 views

The force of wind on baseball

Does anyone know of an equation that I would be able to use for the force of wind acting upon a baseball? I am working on the projectile motion of a baseball with air and wind resistance. I have the ...
1
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0answers
32 views

Pouring Soda At A Constant Angle And Minimizing Filltime While Accounting For $\mathrm{CO}_2$

I was pouring soda, when the act made me think of a question. If you have an unopended $2L$ bottle of soda, and you wish to fill up a generic cylindrical glass cup - if you hold the $2L$ bottle at a ...
1
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2answers
54 views

Can Mars have an oxygen atmosphere?

It is my understanding that, in its gaseous state, oxygen molecules move fast enough to achieve escape velocity. On Earth, we see this more clearly with helium. Regardless of what's happening on ...
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2answers
71 views

How much change in Earth's orbital distance to change average temperature by 1°C?

How much closer/farther would the Earth need to be to/from the Sun to effect a $1 \sideset{^{\circ}}{}{\mathrm{C}}$ increase/decrease in average temperature?
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2answers
25 views

How do you calculate Reynolds and Mach's numbers before solving the Navier-Stokes equations?

Apologies in advance if the question is trivial. I am accustomed to electromagnetics but an amateur on fluid dynamics. My understanding is that the Navier-Stokes equations are solved to determined ...
0
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1answer
51 views

Very Basic Hubble Constant Question

In an article titled "Gravitational Waves Could Solve Hubble Constant Conundrum" Data from the cosmic microwave background suggests the universe is currently expanding at a rate of about 41.6 miles (...
1
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1answer
46 views

Inertia of a falling weight

I use a standard device (penetrometer) that uses a 10 kg weight that is dropped a constant distance to cause a probe to penetrate soil. The penetration distance after 4 blows is recorded. If I were to ...
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4answers
65 views

How much energy is in a 75 kg human being? Including atomic and electrical (charge) [closed]

To calculate the energy in 75 kg of mass is easy with E = mc2. But, how to calculate how much charge are in all our atoms? It is, too, a gargantuan amount of energy.
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4answers
61 views

Bicycle Fuel equivalent on l/100km

Is there a way I can calculate the equivalent how much a Human powered bicycle consumes in the equivalent l/100 Km of Diesel fuel? And also can I calculate the same for Gasoline fuel? And for ...
11
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2answers
1k views

Do variations of the Earth's magnetic field affect gravitational acceleration at Earth's surface, and if yes, by how much?

The Earth's magnetic field varies with time over geological time scales (we have phenomena such as pole inversion). Can this affect the acceleration of gravity at Earth's surface? I would think that ...
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2answers
188 views

How big would a black hole have to be to absorb the Sun?

How big would a slow moving black hole have to be to absorb or otherwise destroy the Sun?
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1answer
45 views

Resistance in fluids

Is atmosphere depth important in reaching terminal velocity in terms of slowing down an object. For instance, if a meteor was dropped from height $h_1$, would it hit the ground with the same velocity ...
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2answers
35 views

Fastest hyperloop-like vehicle which a human could endure [closed]

I'm currently writing on a science-fiction novel where a transportation system like the hyperloop has been built. Now, I'm wondering how fast I can make this. Since the plot takes place on many ...
2
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2answers
60 views

What is the point of generalizing a more specific result to an order of magnitude?

In my textbook, an example wants me to find an estimate of the number of cells in a human brain. It gives the volume of the brain as $8 \times 10^{-3}\ \rm m^3$ which it then estimates further as $...
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2answers
144 views

Is it possible to have a planet entirely made out of liquid water?

Earth is mostly covered in oceans, but they only go a few kilometres deep. It's obviously not possible to have a planet the size of the earth to be made entirely out of water, because of the kind of ...
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2answers
59 views

How far can you pee on the moon vs. mars? [closed]

Let's suppose you are at Elon Musk's Future Mars colony and you drank too much beer, how far can you pee on Mars if you can pee one meter on earth? If the next day you get on the shuttle to the ...
1
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1answer
39 views

Is 1 lux unrealistically low for a cell phone camera flash?

I have a light source which is similar to a typical cell phone camera flash. Based on a measurement and some calculations, I estimated that its illuminance is about 1 lux, or close to twilight values ...
0
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2answers
73 views

Time for black body to cool to a given temperature

I'm trying to figure out the time required for a blackbody to cool assuming it only looses heat via radiation. I can estimate the mass, specific heat, surface area, emissivity, initial temperature, ...
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1answer
61 views

Gamma Photons vs. Muons; Which is more expensive [closed]

Which one takes more energy to produce? I ask as I theorize that keeping the plasma in a fusion reactor is very expensive. Muons, while useful, are too short lived. Maybe... Keeping the plasma at ...
4
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1answer
47 views

How long for released dye to uniformly saturate the oceans?

Suppose a supertanker filled with purple dye breaks open at a particular point in the middle of the Pacific Ocean and spills an enormous volume of purple dye into the ocean all at once. Imagine that ...
0
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0answers
31 views

What formulas do I need to calculate the time it takes for a room with opened window to become the same temperature as outside?

I want to calculate how long I have to open my window to become the same temperature as outside. To make things more easy let’s assume there’s almost no wind helping the exchange of temperature.
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2answers
44 views

Calculation of Gravitational Collapse time

The answers to Gravitational collapse and free fall time (spherical, pressure-free) describe the calculation of collapse time for a gas. For the case of neutral hydrogen gas with number density $10^4$/...
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0answers
5 views

Calculate weight of a barbell via measurement of period of oscillations

I have seen some videos on YouTube about some people that use "fake weights" in the gym, declaring to be able to lift much more weight than what is actually on the barbell. However, I think it should ...
10
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3answers
3k views

How would a fast-moving atom interact with a body? [closed]

I found this question on Quora: https://www.quora.com/Can-you-theoretically-shoot-an-atom-fast-enough-to-kill-its-target I think the Quora answer is good but incomplete, and it got me wondering what ...
71
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13answers
21k views

If visible light has more energy than microwaves, why isn't visible light dangerous?

Light waves are a type of electromagnetic wave and they fall between 400-700 nm long. Microwaves are less energetic but seem to be more dangerous than visible light. Is visible light dangerous at all ...
2
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1answer
49 views

If I drive East, how much lighter am I than if I drive West?

I'm at the equator. Suppose I am driving at x kph, in the direction of the Earth's rotation (i.e. due East), I presume that the force my vehicle exerts on the ground is less than when I am stationary. ...
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2answers
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1answer
87 views

How to get the radius of Bohr from the uncertainty principle?

I would like to know how to get the following result: \begin{eqnarray} a_0=\frac{4\pi\varepsilon_0 \hbar^2}{\mu e^2} \end{eqnarray} from the beginning of the uncertainty of heisenberg. If possible, I ...
2
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2answers
177 views

I'm travelling near the speed of light. Do I need to brake before using a super-massive black hole to turn around?

I'm taking one of those new fusion drives for a trip to nearby supermassive black hole. At a comfortable 1 G, it'll take me about 7 months of proper time to accelerate to 95% the speed of light. I'm ...
22
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6answers
6k views

Why does shooting a handgun accelerate a bullet to deadly speed without injuring the gun user's hand?

Momentum is defined by the product of mass and velocity. Now a projectile out of a gun has to have high velocity to penetrate a human body, as its mass isn't significant. But to reach this velocity, ...
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2answers
77 views

Do comets and meteors attract artificial satellites while passing by?

What will be effect on artificial satellites when comets or meteors come close or pass by?
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1answer
40 views

Laser guns and scattering

I recently read an article that explained how the US Navy would like to use laser guns in the infrared region, with a high power - 500,000 W I guess. However, because of Rayleigh scattering that ...
0
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1answer
47 views

Cycling: The energy behind it

I'm developing a school project (I'm studying software engineering) and it's about a sharing bicycles company. We need to calculate the total amount of necessary energy to travel from one point to ...
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2answers
51 views

Is lift force proportional to size?

I'm trying to calculate lift force of a particular object I'm working with. However, I can't find much information on how much force is required for an object to stay in flight though. My questions ...
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1answer
43 views

Casimir effect - gravitational influence?

Regarding the Casimir effect, is gravitational attraction too weak in order to explain the attraction between the plates?
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1answer
67 views

Is it possible to use an accelerator/collider as a space engine? [closed]

I was just trying to get a discussion going about physics that we can already create. I did not realize that I would have to write a paper to ask a simple question. Is it possible to use an ...
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6answers
8k views

What is the probability for an electron of an atom on Earth to lie outside the galaxy?

In this youtube video it is claimed that electrons orbit their atom's nucleus not in well-known fixed orbits, but within "clouds of probability", i.e., spaces around the nucleus where they can lie ...
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1answer
178 views

Electric force is stronger than gravitational force yet gravitational forces holds the Sun and planets in their orbits around the Sun [closed]

The electric force between an electron and a proton, between two electrons, or between two protons is much stronger than the gravitational force between any of these pairs of particles. Yet even ...
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0answers
72 views

Approximate probability of a person's wavefunction collapsing to the moon?

As a sort of introductory concept to quantum mechanics, I've heard many explain that there's a small but nonzero probability of unlikely events happening: your hand quantum tunnels through the desk, ...