The property of an object that determines how much it responds to a force in Newtonian mechanics, and how much it interacts with gravity in the Newtonian framework. Mass also refers to the intrinsic energy of a particle in particle physics.

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267 views

Find the center of mass of a hemispherical shell

Problem: Find the center of mass of a hemispherical shell of constant density and inner radius r1 and outer radius r2. Attempt at Solution: Let the hemisphere be in the region $z>0$. By symmetry, ...
4
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2answers
213 views

Origin of quark masses

Does all the mass of the quarks in the standard model come from the Higgs sector or is there also a contribution to quark masses due to QCD chiral symmetry breaking?
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6answers
946 views

Is (rest) mass conserved in special relativity?

I don't understand why it is said that the (rest) mass of a system is not conserved in relativity. I mean, the momentum of a system is conserved (i.e.: it remains constant in a frame of reference ...
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28 views

Is density of a material related to penetration?

Theoretical question. If you have a standard projectile with mass 1 and velocity 1 and fired it at different materials would the penetration be related to the density of the material? I'm not trying ...
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2answers
113 views

How can a photon have energy when its mass is zero? [duplicate]

How can a photon have energy when its mass is zero? According to Einstein's equation $E = mc^2$ energy depends on $mass*c^2$ Light has zero mass so the energy would be zero too but solar cells use ...
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2answers
57 views

Does the gravitational force of one object interfere with that of another?

Assume we have two iron spheres, Sphere A and Sphere B, with identical masses floating in the vacuum of interstellar space separated by some distance from each other. The gravitational force of each ...
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1answer
144 views

How can the Schwarzschild radius of the universe be 13.7 billion light years?

So i was reading about Schwarzschild radius on Wiki and I found a interesting thing written there link. It says that the S. radius of the universe is as big as the size of the universe? How is this ...
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2answers
115 views

Does mass curve space?

Just to be sure, according to the theory of General Relativity, my understanding is that mass curves space-time. My question is, can mass also curve space?
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4answers
173 views

What exactly is the mass of a body? What determines it?

The term "mass" is very common. But what does it depend on? How is it known?
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129 views

Deriving the Lorentz factor

Recently, I learned how to derive E = mc^2. However, to do so, one must accept the relativistic mass equation. How does one derive this?
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80 views

Are black holes an infinite source of energy? [duplicate]

Black holes are considered particularities because in a determined point in time they are pointless, as consequence there are some mass in a null space so the density become infinite. Finally if ...
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3answers
190 views

Uniqueness or multiplicity of ADM masses for spacetime manifolds with more than one “end”?

The question is: What is the mathematical and/or physical basis for saying that a (static) spacetime manifold with more than one asymptotically flat region at infinity ("end") has a distinct ...
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1answer
257 views

Is $E=mc^2$ false?

Recently, I found a YouTube video saying that $$E=mc^2$$ is false. It says that the real one is $$ E^2=m^2 c^4 + p^2 c^2 $$ where $E$: energy, $m$: mass, $c$: speed of light and $p$: momentum. Is ...
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63 views

Mass of NGC 1097 Galaxy

I've been looking all over the internet for this and can't seem to find a reference. Can anyone refer me to a paper citing the mass of NGC 1097 based on luminosity?
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66 views

Metric in Lagrangian and the minimum total potential energy principle

I was wondering why physical systems "like" to go to the minimum of potential energy and I found this question, that tries to justify the minumum total potential energy principle. I was also reading ...
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0answers
26 views

Interpretation of Mass Continuity Equation in MHD [duplicate]

I'm writing up my final-year dissertation and I'm required to give, as part of the introduction, an analysis of all the equations (and their terms) of which I use. Embarrassingly, whilst of course ...
43
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5answers
6k views

Why is the prospective new kilogram standard a sphere?

I can understand the choice of material, silicon 28, but why is it a sphere rather than (say) a cube? Article here I would have thought that a sphere would have been the hardest shape to machine ...
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80 views
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74 views

Smallest Black hole nessesary to devour Earth?

While looking into black holes I can across the idea of hawking radiation, and the fact that microscopic black holes would near instantaneously evaporate before doing any damage. However larger black ...
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1answer
353 views

What is the center of Earth's landmass? [closed]

I have read, several times, that the Great Pyramid is located at "the center of Earth's landmass". How do we define "Earth's landmass"? And once defined, how do we find the center of it?
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1answer
4k views

Calculate mass of air in a tyre from pressure

How can one calculate the mass of air inside a tyre, given a particular tyre size; a pressure, in $kPa = \frac{1000kg}{m\cdot s^2}$; and assuming room temperature, and normal air composition? I can't ...
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1answer
69 views

What it would look like to observe people with a different time flows?

As I learned, that the bigger gravity source you are influenced by the more slow time ticks for you, the farther away you are from a gravity source the faster times ticks. So Imagine two different ...
4
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1answer
86 views

How much mass is typically ejected from a supernova?

How much mass is released from a supernova of a 15 solar-mass star? 20? 25? What is the relation between star mass and mass ejected?
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0answers
44 views

What happens to the d/dr term of the continuity equation in cylindrical coordinates?

The derivation of the continuity equation in cyclindrical coordinates should look like this, $$ \dfrac{dm_{cv}}{dt}=\sum \dot{m}_{in} - \sum \dot{m}_{out} $$ where $$ m_{cv} = \rho r ...
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1answer
43 views

Is it possible to calculate the information content of matter? How?

I know the Bekestein bound is the upper bound for the information content of a region of space, but is it possible to actually calculate that information content (number of bits, not the bits ...
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1answer
68 views

Real-world evidence that non-massive entities (or even: antiparticles), and their behaviors, are sources of gravity?

The theory of general relativity tells us that non-massive entities, and their behaviors, are possible sources of gravity. Mass isn't needed, the theory says. What's the real-world evidence that ...
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33 views

How can I compare magnetism/mass ratio of different magnets?

I want to compare the magnetism/mass ratio of different magnets. Let, for example be ceramic/samarium-cobalt/alnico/steel/neodymium magnets. Questions: What units should I compare for ...
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1answer
81 views

Heuristics for the Hawking mass

I have the following definition of Hawking Mass. Given a spacelike 2-surface $S$ embedded in a 3+1-dimensional Lorentzian Manifold $L$, $$ M(S) := \sqrt{ \frac{\text{Area}(S)}{16 \pi}} \left(1- \frac ...
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1answer
60 views

Spring pulled with one end fixed [closed]

As the title says, if one end of a spring of mass $m$ is fixed to say, a wall, and the other one is pulled at a constant velocity $v$ by some external agent, we have to find the kinetic energy of the ...
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1answer
87 views

Wouldn't dark matter throw off the calculation of Earth's 'light' mass and estimates of its composition?

The Cavendish experiment first determined the mass of the Earth and (arguably) the gravitational constant. However, given the ubiquitous nature of dark matter, it seems reasonable that at least some ...
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2answers
73 views

Is there any gravitational force between two stationary neutrinos, a billion light years apart?

Gravity is supposed to act over an infinite distance. But if the force is very weak (due to low masses) and the distance is very far, is the force actually 0? Or is the force so low that it is ...
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2answers
113 views

Motivation for Negative Mass

Lately I've been reading a little bit (mostly here and on Wikipedia) about exotic matter, particularly matter with a negative mass. This question appears to be the original question on the site of the ...
4
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1answer
91 views

Range Of An Interaction

Why is the Compton wavelength $\lambda_c=\frac{\hbar}{mc}$ used as a sensible measure for the range of an interaction, where $m$ is the mass of the corresponding mediator?
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7k views

Why can't photons have a mass?

Why can't photons have a mass? Could you explain this to me in a short and mathematical way?
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1answer
70 views

Why do massive force carriers result in short range forces

I've been reading the answers to a few questions relating to force carrier particles, and it has been mentioned that massive force carriers always result in short-range forces, while massless carrier ...
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0answers
42 views

Total Mass in Universe [duplicate]

Currently (2015), what is the total mass of the universe? How can we say with mathematical certainty that 69% is dark energy; 25% is dark matter; 5% is atomic matter; and 1% is neutrino, photon, and ...
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4answers
3k views

Do all massless particles (e.g. photon, graviton, gluon) necessarily have the same speed $c$?

I suppose there was a discussion already on speed-of-gravity-and-speed-of-light. But I silly wonder whether all the massless mediators of four fundamental forces, i.e. Graviton: $g_{\mu\nu}$ ...
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1answer
56 views

How to find the centre of mass of 3 masses (astronauts and a rock) connected by a rope

To be more specific on the problem, a 50kg astronaut, an 80kg astronaut and a 20kg rock are tied together by a light rope during a space walk. I am asked to find the center of mass. Now, I've chosen ...
2
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1answer
281 views

How can I determine the pound-force behind a punch?

I am a martial arts instructor always looking for the next best way to enhance the performance of my students. However, I'm having difficulty understanding how to determine the pound-force (ibf) of a ...
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1answer
70 views

Particle with 1 GeV mass?

I know a proton as a mass of 0.938 GeV also neutron at 0.939. But I was wondering if there is anything with a measured mass of 1 GeV? Or, whether a proton can have a mass of 1 GeV within a system (as ...
0
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1answer
27 views

Will all the mass collapse in one place?

Will the stars, planets and everything in the universe collapse due to the gravity? Or does the constant expansion of the universe break that idea ? What will happen with the energy?
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1answer
89 views

How to calculate the energy required to rotate a planet?

How to calculate the energy required to rotate a planet from non-rotating state? Say the planet is Venus with equally distributed mass of $4.8676 \times 10^{24}$ kg, and desired rate of 1 rotation per ...
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0answers
36 views

An interesting question on the mass of a droplet of liquid experiencing the Leidenfrost Effect

Background and Inspiration: I have seen numerous demonstrations of the leidenfrost effect, both on the internet and in my mother's kitchen. But I started wondering about a general case after having a ...
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2answers
115 views

What is the fastest speed that a massive object can travel at? [duplicate]

What is the fastest speed (in miles per hour) that a massive object can travel at? I have heard that an object can travel at the speed of light, but I've also heard that massive objects cannot travel ...
2
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1answer
93 views

Is it possible to have a black hole in empty space?

If the escape velocity of two very massive objects is near the speed of light, and those objects are orbiting each other (let's ignore the Roche limit for this exercise), is it possible that the ...
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5answers
2k views

Why aren't all black holes the same “size”?

The center of a black hole is a singularity. By definition, a singularity has infinite density. So how can a black hole with a different mass or density be described?
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7answers
3k views

Does electron in wave form have mass?

I heard from my lecturer that electron has dual nature. For that instance in young's double slit experiment electron exhibits as a particle at ends but it acts as a wave in between the ends. It under ...
12
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3answers
13k views

How do we determine the mass of a black hole?

Since by definition we cannot observe black holes directly, how do astronomers determine the mass of a black hole? What observational techniques are there that would allow us to determine a black ...
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1answer
73 views

Is my calcualtion from the mass of a photon right? [closed]

The Mass off a Photon The right format can be found here: Photon E = hv E = mc2 E = av (amplitude, frequency) m = hv/c2 Mass = movement of electromagnetic fields Planck’s constant = electromagnetic ...
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51 views

Dynamic mass or static mass?

I am testing a cantilever beam assuming it as a single degree of freedom system, therefore it can be described by the equation $$m_d \ddot{y}(d) + c_d \dot{y}(d) + k_d y(d) = p(t) $$ Where $d$ is ...