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Questions tagged [order-of-magnitude]

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What are simple comparisons of energy draws? [on hold]

I have recently attended a Bitcoin mining conference. Some of the attendees were specialists in energy with their business being oriented around building data centres or catering to the needs of data ...
75 views

The answer to this question is not close to the age of the universe, then why do we say it is?

I saw this question in our textbook A great physicist of the century (P.A.M. Dirac) loved playing with numerical values of Fundamental constants of nature. This led him to an interesting ...
128 views

Why does everyone seem to assume that gravitational waves will always be very small? [duplicate]

The size or effective distortion field of a gravitational-wave perturbation at any given location in space-time is determined by the distance separating the source and that location. This describes a ...
69 views

Order of magnitude radiation measures conversion?

Standard unit of ionizing radiation dose is Sievert. I can get a rough idea of how dangerous absorbing various amounts is from https://xkcd.com/radiation/ and other sources. There are many other ...
12 views

How to compare scales in a thermodynamic system

Suppose we have a generic system with hamiltonian \begin{equation} H= JH_1 +\mu H_2 \end{equation} where $J$ and $\mu$ are couplings and $H_1$ and $H_2$ are just two dimensionless parts of the ...
56 views

Why does the universe manifest scale?

I'll try outline my question in clear terms, articulating specific aspects that are its primary motivators. I'm just beginning in my exploration of physics as a student, but a persistent question that ...
125 views

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
28 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 ...
40 views

Sun's energy and grand unification

According to Wikipedia, The approximate grand unification energy value is equal to $1×10^{25}$ eV or $10^{16}$ GeV This is equal to $1602176$ J. Now, The Earth receives 174 petawatts (PW) ...
65 views

When is the order of magnitude not equal to the exponent of scientific notation?

Explain why the order of magnitude is sometimes not the same as the exponent in scientific notation. It is because of the units?
114 views

When do you use Quantum Mechanics? [duplicate]

Given a problem, how does one know whether to use quantum mechanics or classical mechanics? Take for example electron scattering from a nucleus. The electrons are given a wavefunction in this case. ...
160 views

Where is the line between Quantum and Relativity?

Its often said QM is for the very small and GR for the very large. This brings to mind that there should be some limit at which one starts to apply and the other stops. Now I know there are more ...
43 views

Different approch on Order of magnitude confusion [closed]

My problem: How many orders of magnitude larger is the sun $(1.99$ x $10^{30} kg)$ than the moon $(7.32$ x $10^{22} kg)$. Justification 1: So according to my teacher, we can do this question by ...
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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 ...
400 views

Quantity of force between two magnets

I have compiled data detailing a magnetic field. If I assume a duplicate magnet is set up across from it, how can I calculate the repulsive force between them?
382 views

How do you quantify the “much greater” operator “$\gg$”?

I'm specifically asked to compute the charge in the Earth-Moon system knowing that the gravitational force between the two bodies is much greater ($\gg$) than the electrostatic one. However, I don't ...
153 views

Mammal Population Estimates as a Fermi problem [closed]

Can We estimate the order of magnitude of number of mammals on earth? Can this be treated as Fermi problem or not?