Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [estimation]

The tag has no usage guidance.

0
votes
2answers
46 views

Can average acceleration be exactly determined from discrete points separated by equal time intervals?

My question: is there an exact expression for the time-average of acceleration in terms of projectile position coordinates measured at instants in time separated by a constant, known time period? I ...
0
votes
0answers
22 views

How cold does Something need to be for String Theory to be relevant?

I’ve often read casually that in order for modern string theory and other competing quantum gravity theories to be tested absolutely enormous temperatures (or rather energy densities) are required. ...
-2
votes
0answers
26 views

Atmospheric dynamics [closed]

Assuming that bathtub is 1.5m long and that typical velocities in the water are about 1cm/sec.The bathtub is at situation at an area of 24°S. Use the concept of scale analysis and Rossby number to ...
54
votes
11answers
17k views

Why don't solar panels contribute to global warming?

I've been wondering this for a while but I have not yet encountered an explanation. This is from my understanding of physics, which is by no means expert, so sorry for my crude explanation: Energy ...
28
votes
4answers
13k views

If an apple is magnified to the size of the earth, then the atoms in the apple are approximately the size of the original apple

Quoting from the Feynman Lectures on Physics - Vol I: The atoms are 1 or $2 \times 10^{−8}\ \rm cm$ in radius. Now $10^{−8}\ \rm cm$ is called an angstrom (just as another name), so we say they are ...
2
votes
1answer
55 views

Can the Earth's negative charge make negatively charged objects levitate?

Since the earth's surface has a negative charge, could it repel a large highly negatively charged body? An example is an object on stilts carrying a negative charge that is heavier than air, maybe ...
0
votes
3answers
87 views

Is it possible to use force to reduce the empty space in an atom?

Atoms are mostly empty space (at least from what I've heard) so is it technically possible to shrink the space between the electrons and the nucleus of an atom?
0
votes
1answer
38 views

At what rate does the typical human body sink in a swimming pool? [closed]

Let's say I'm $1.8\ \rm m$, $70\ \rm kg$ with a fairly typical male body shape. I hold on to the side of an otherwise normal but very deep swimming pool, then lower myself so that the top of my head ...
-1
votes
1answer
39 views

Estimating the minimum hole size for leakage through a sealed membrane [duplicate]

Suppose I have a thin membrane sealed onto a flat surface along its perimeter, and there is water between the two surfaces with a certain pressure $P$. I would like to know, if I made a circular hole ...
1
vote
0answers
44 views

How can I calculate the impulse caused by a nuclear bomb on structures?

I want to calculate the impulse caused by a nuclear bomb on structures. Is there a function that I can use to calculate the amount of impulse acted upon by a nuclear bomb depending on its size? Also, ...
-1
votes
1answer
82 views

What would happen if gamma-ray burst from a supernova burst hit the sun? [closed]

What would happen if gamma-ray burst from a supernova burst hit the sun? Would the sun explode? Would the sun expand. Have a longer lifetime? Shorter Lifetime? Because people are nit-picky about stuff ...
31
votes
1answer
3k views

Does more light from Andromeda get scattered in the atmosphere than in the entire trip to Earth?

Fires have been burning here in Northern California. Today there was just a slight haze of smoke. The sun had a slight red hue to it. As expected the lower it got the redder it became. The blue light ...
8
votes
1answer
180 views

What would really happen if somebody dropped a small black hole into the Earth?

Suppose we drop a small black hole, but large enough that it accumulates mass more quickly than it radiates it, into the Earth. What happens? This question has already been asked here and here, but ...
2
votes
3answers
78 views

If a drop of water hits something at bullet speed, will it damage it?

I can't find this anywhere. If a drop of water hits a glass for example, at the speed of a bullet, will it damage it? Or will it just make the same as a raindrop?
-1
votes
1answer
61 views

How many calories in a block of wood?

I was recently thinking about the human body and the energy we get from food. I understand we don't have the ability to properly digest certain things like stones and wood and grass, but if we did, I ...
-1
votes
1answer
49 views

Looking at Earth's history using a cosmic mirror [duplicate]

Assuming we have a very powerful telescope, and a huge mirror 1000 light years away from earth, is it possible to look at this mirror to see what people did on earth 2000 years ago? Is it even ...
1
vote
2answers
134 views

Bullet hits Earth at speed $0.99c$ [closed]

According to wikipedia, the speed of the neutrino is as close as we can get to the speed of light with an object with rest mass. As per the comments, since neutrinos come in different energies, let's ...
-3
votes
2answers
50 views

What if the luminosity of Sunlight increased by 10% [closed]

If the luminosity of sunlight increased by 10%, would people be able to survive outside? Would such brightness of light be very harmful to them, for exemple as much as the Mercury Vapour Lamp without ...
-2
votes
1answer
56 views

What is the force behind this punch? [closed]

I originally asked this in worldbuilding due to the context, though I suppose it's just a physics question. I was never great at physics in school but let's say there's a super human and they're ...
0
votes
2answers
105 views

Effectiveness of cooling oneself by a hand fan

I recently had a discussion with a friend of mine regarding the effectiveness of handheld fans. My friend argued that you would always get warmer. I’m sure that this needn’t be the case, as the system ...
1
vote
1answer
28 views

How much stress do Elephants feel due to weight?

While we humans weigh around 70 kgs , Elephants weigh around 5000 kgs. My question is :While moving or standing ,how many more times than humans does the Elephant feel the stress due to weight? Is ...
0
votes
1answer
74 views

Collision Speed at which seatbelts become ineffective [closed]

In a car, what is the speed at which if you were to crash (eyeballs-out) your deceleration would be so high that your seat belt becomes ineffective and that you would've die whether or not you ...
16
votes
3answers
3k views

Does the Earth's rotation affect redshift measurements?

How do you account for the spin of the earth in the mechanical sense, when measuring redshift? Does the relatively slow speed of the earth have a major change in the measurement because of distance?
0
votes
1answer
176 views

Why trains are not heavy? [closed]

I have seen a video on youtube where Feynman explains that engines of trains are heavy to compensate for the fact that steel has a low coefficient of friction. But, whereas this seems plausible for ...
1
vote
1answer
35 views

Whats the energy spent on a push-up? [closed]

Let a human of height 1.80 m, arm length of 0.5 m and weight 80 kg do a push up. How much energy did she spend? $$ F = m \cdot a $$ $$ E = F \cdot s $$ $$ \rightarrow E = m \cdot a \cdot s,$$ where $...
-2
votes
1answer
50 views

How loud would a sound have to be for it to travel the distance of Pittsburgh, Pennsylvania to New York, NY? [closed]

I'm just wondering if it's possible, more than anything. But if it is, how many decibels would the sound have to be to travel that far of a distance?
8
votes
2answers
2k views

How far can a shout travel?

I was wondering, if a person climbs a tower and shouts at the top of his lungs how much distance would the sound travel ? Would it reach someone 1km far? Assuming that there are no tall buildings in ...
35
votes
1answer
9k views

Can I eat myself into a black hole?

This was a humorous thought experiment that occurred while chatting about black holes. The person that I was talking to assumed that a black hole required a specific density to be achieved. I pointed ...
6
votes
3answers
176 views

Dam Son's problem: how long does it take to boil an ostrich egg?

The egg boiling problem is a seemingly simple problem posted from the blog of UChicago's physicist Dam Thanh Son. A chicken's egg has a length of 5 cm and takes 6 minutes to boil. An ostrich'...
0
votes
1answer
97 views

How loud is the sun? [duplicate]

The sun is a continuous explosion. The reason we cannot hear the sun is because of the vacuum separating us. If that space was to be filled with air, would the sun be audible?
-1
votes
2answers
55 views

How large of a capacitor is needed to hold 5,000,000,000 J? [closed]

Given today's technology, what size of capacitor (in farads and physical size) would be required to hold 5,000,000,000 J of energy, the estimate for the amount of energy in the average lightning bolt?
1
vote
4answers
114 views

How the Heisenberg principle holds for protons?

Does this principle holds for protons since their position is, in a manner of speaking, known and they are also assumed to be stationary at every popular physics book that I have read, including the ...
12
votes
4answers
2k views

What if the Chelyabinsk meteor had been a black hole of equivalent mass?

The Chelyabinsk meteor is estimated to have had a mass of 10,000 - 13,000 metric tons. A black hole of mass $13\times10^6\ \mathrm{kg}$ has a radius of $$ r = \frac{2GM}{c^2} = \frac{(2 \times 6....
0
votes
0answers
41 views

Can you destroy the Sun if you throw enough iron into it? [duplicate]

i have a vague understanding of how the inside of the sun works, but i remember from class that when the sun started "making" iron on it's core, it cannot go further; can't make a heavier element. ...
2
votes
1answer
43 views

Standard deviation and single errors of measures

During my courses of laboratory, we used as a rule of thumb the following statement: If you have less than five measurements (each of them with its error), the error of the mean is simply the squared ...
5
votes
4answers
192 views

What would happen to a 10 meter sphere of room temperature water if released into space?

Imagine that we had a space station with a relatively large hangar, and we allowed a ball of water to accumulate that had a 10 meter diameter and a water temperature of 20C. While the hangar is ...
9
votes
4answers
7k views

Can a 1 watt heating element boil water? [closed]

If I take a 1 watt heating element, put it in a glass of water and I put them both inside a sealed imaginary chamber that does not conduct heat outside (again, imaginary). Will the water eventually ...
0
votes
1answer
36 views

Estimating the viscous drag of a moving floating body

I am interested in the viscous drag of a floating body (let's say an cylindrical iceberg in water) moving with a constant velocity, s.t. the Reynolds number of the fluid is very large. I am taking a ...
13
votes
2answers
496 views

Should we take the elevator instead of the stairs to save energy?

In our university there's a posted sign that encourages students to take the stairs instead of the elevator to save the university electricity during the hot NYC summers. When you climb the stairs ...
0
votes
2answers
103 views

Why was the glass broken in the Lobby but not above the impact zone? - 9/11

Disclaimer: I do thoroughly believe that 9/11 was a terrorist attack, so please don't start arguing whether it was an attack or inside job, focus on the question. Also: I was about to post this in ...
-3
votes
1answer
57 views

Could enough people spin Earth backwards faster than they could run? [duplicate]

So, consider the theoretical situation in which the earth is no longer spinning, and we want to spin it up by running in the opposite direction (Yes, this question was inspired by the Nike commercial)....
6
votes
2answers
111 views

What would the sky look like if the Sun was a black hole?

As a complement of this Phys.SE question. What kind of lensing and diffractions effects from space would be perceived on earth?
0
votes
2answers
183 views

Linear or Quadratic Air Resistance

I'm trying to model a rocket's position with air resistance as a factor. The rocket is fairly low-powered (Estes A8-3, 9.7N of thrust for 0.7 seconds), and I estimate it won't be going faster than 50 ...
1
vote
1answer
57 views

What is the variance associated to the average gate fidelity?

Let $U$ be a unitary and $\mathcal E$ a map on a space of dimension $D$, and say we want to assess how "close" $U$ is to $\mathcal E$. A standard way to do this is using the average fidelity $\...
1
vote
2answers
46 views

If you are ontop of a giant heavy object that is falling from the sky, is it possible to jump and roll at the perfect time to survive? [duplicate]

I don't know if gravity or the speed of the drop would prevent us from jumping, but would something like this be possible? If it's not possible on the ground, is it possible in the ocean? I'm sorry ...
3
votes
1answer
95 views

Minimum size of a “water star”

So I had this weird idea the other day. We know that stars form from simple matter (dust, gasses, etc) forming a gravity well, attracting to each other, until the amount of mass and density in the ...
2
votes
3answers
78 views

How to calculate the Sun’s energy output? [closed]

What formula can be used to find the total energy being produced from the Sun in Joules per second? If I recall correctly, the energy is around $2.3012 {\cdot} {10}^{27}\,\frac{\mathrm{J}}{\mathrm{s}}...
0
votes
1answer
63 views

Could an object orbit a person's body? [duplicate]

Imagine you were on a spherical spacecraft that had equal mass all the way around and you were deep in space, away from the gravitational pull of any planetary bodies or stars. If you released a ...
2
votes
1answer
42 views

How much faster is the chain reaction in a power plant than that of natural uranium ore? What about a nuclear bomb?

How much faster does the fissile uranium in a power plant 'break down' than an equivalent amount of naturally decaying U-235? How much faster is the chain reaction in a bomb compared to a power plant?...
0
votes
1answer
31 views

Is the mean CBM frequency more red-shifted since discovered in the 1960's?

If the universe is uniformly expanding at rate x, is possible to measure that the CBM has increased its red-shift value over time? If the red-shift is a static value, is it possible that the ...