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Questions tagged [mass]

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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6answers
143 views

Formulation of Newton's second law: $F=ma$ or $a=\frac{F}{m}$?

Assuming a constant mass, which would be best way of expressing Newton's second law? $F=ma$ or $a=\frac{F}{m}$? The most common way is the first one, but I feel more comfortable explaining it the ...
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What is heavier, water or ice?

I was reading this link and I never saw a definite answer. One would think if you have 1000 pounds of water, and you froze it and weight it you would still have the same 1000 pounds of water when ...
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38 views

Pendulum: Time period for effective length varying with angle

For a pendulum whose effective length changes with angle, my approach would be to write the length as a function of the angle: $\ell(\theta)$, then using the torque derivation of the time period I do ...
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1answer
47 views

Has the gravity a negative value?

We all know that the acceleration of the gravity is equivalent to 9.81 m/s². But the gravity attract everything that have a mass (everything as far as i know) to the center of a planet. As an ...
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1answer
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Rate of angular momentum at the center of mass

I'm currently trying to calculate the Zero Moment Point for a game I develop, however im terrible at physics and therefore have trouble calculating the “rate of angular momentum at the center of mass”....
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2answers
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Does the length variable in pendulum motion include center of mass?

In diagrams, is the bob/mass of the pendulum considered a point, or a 2/3D object? And furthermore, is the length variable in the period of a pendulum simply the length of the string, or is it really ...
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1answer
71 views

2019 Higgs Boson Mass?

Wiki, based on the 2018 Particle Data Group, gives the Higgs boson mass as $125.18 \pm 0.16$ GeV$/c^2$. OK. However, 2017 ATLAS gives a combined value of $124.98 \pm 0.28$ GeV$/c^2$. So what is ...
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1answer
37 views

What is the Komar mass of the de-Sitter spacetime?

The Komar mass of some spacetime is defined as an integral (volume or surface, depending on its formulation): https://en.wikipedia.org/wiki/Komar_mass The de-Sitter metric in static coordinates is ($\...
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42 views

What's the most likely mass for ethanol?

I am interested in learning a little about mass defect and calculating the molar mass of ethyl alcohol. I found this table of atomic weights and would like to use it to compute the mass of the ...
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24 views

Transferring Kinetic Energy - a worldbuilding physics question

I'm working on an RPG for some friends and I'm curious about a magic system I'm thinking of designing and how it would interact with physics. Please bear with me as I'm neither mathsy nor a physicist. ...
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56 views

Relativistic mass of particles

My question is about aquiring mass by particles moving at speeds comparable with $c$. Is this somehow related to the logic that a force field that is moving in planck waves towards a body that is slow ...
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Deriving relation between pole and running quark masses

How do I compute quark self energy and use it in order to derive detailed relation between pole and running quark mass? If I do it for one loop, I should use this for running mass: $\mu^2\times\...
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1answer
39 views

Why can't a Weyl Fermion have mass?

My understanding was that a particle may have mass if there is a quadratic term in the fields without derivatives. For a single left-handed Weyl fermion, the following expression is lorentz invariant, ...
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Is there a difference between a electronic force restoration balance and a Kibble balance?

At least from the description of the working principle, the typical analytical balance seems to use the same principle used by Kibble - Watt balance to realize the international standard kilogram from ...
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4answers
53 views

Why don't we always lift stuff from center (center of mass)?

if you lift a large box alone, you try to lift it from the Center(Center of mass),but if the box is small you just use both of your hands each grabbing a side of the box(not from center of mass). if ...
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1answer
38 views

Is the centre of charge always within the centre of mass of an object?

What I am confused about is whether the charge of an object is concentrated within the centre of the mass itself, or does it change depending on the situation?
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1answer
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$H_2O$ vs $2H^+ +O^{2-}$

I am wondering the mass deficit between 2*H + O and H2O. I.e. if I would know the accurate mass of one atom of hydrogen on it's own and the mass of one atom of oxygen on it's own how much of a ...
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4answers
108 views

Is mass persistent in spacetime?

As an object moves through spacetime is its mass persistent? What I mean is, if we find a way to look backwards into time, will a pen sitting on a desk when I was in college still be sitting on that ...
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1answer
69 views

Possible proof that the universe can not have infinite mass? [duplicate]

I was thinking about the possibility of the universe having infinite mass, but then it occurred to me that it would then perhaps violate conservation of mass. Here is my thought process: Assuming ...
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1answer
65 views

Does $E=mc^2$ apply to electron shells with different energies? [duplicate]

Is this statement true: Each electron shell has a different energy level, with those shells closest to the nucleus being lower in energy than those farther from the nucleus. Mass of electron $= 9....
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1answer
30 views

What is the total mass of orbiting interplanetary unbound atoms in the solar system?

Excuse the poor phrasing of the title, but it became apparent to me that the solar system has some degree of density (i.e it is not a perfect vacuum). So my question is if any of these particles (not ...
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0answers
71 views

What would be the properties of an anti-black hole (concentration of negative mass)?

What would be the properties of an anti-black hole (concentration of negative mass)? Would it emit radiation? Would time go infinitely fast on its surface?
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1answer
27 views

Can the ADM mass be defined locally inside a closed surface?

To calculate the ADM mass, one has to specify a closed surface inside which all the mass is located. Are there any ways to calculate the mass inside a closed surface outside of which other mass still ...
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1answer
29 views

Mass and energy of radiation

We know that mass can be  converted to energy and vice versa. So does the mass of molecules or atoms change when they absorb a radiation and go to the higher energy state?
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1answer
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Will gravitational field of a body increase if the body is accelerated? [duplicate]

Suppose a body is at rest of mass m. If the same body is accelerated at velocity v, the mass increases to some definite amount. Since the mass of the body has increased, will the gravitational field ...
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1answer
76 views

Black hole mass

It has been taught to us that since the black holes have finite mass, their gravitational force is also finite, which totally fits. The Black hole anyhow has a singularity at it's center which is ...
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1answer
32 views

What is the significance in determining the mass of a black hole? [closed]

Was just wondering the importance of the mass of a black hole
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Paradox regarding phase transitions in relativistic systems

The main question I would like to ask is whether quantities such as density are dependent on the frame of reference. I have searched several forums and the answer is somewhat controversial. Some ...
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0answers
55 views

How to estimate the mass of an incoming asteroid?

A second galactic visitor has just been observed: see this link. For a mass which is small enough to have no noticable effect on other masses, is there any other way to infer the mass? Its own motion ...
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2answers
60 views

Does light have mass? Why? [duplicate]

I've been wondering whether light has mass. Yet given the wave-particle duality of light, the statement seems to be affirmative. With that, how to calculate it?
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1answer
35 views

Is there a Mass-Temperature relationship for main sequence stars?

When finding relationships between various properties of stars, I frequently find next to nothing on the Mass-Temperature relationship. I, of course, see the Mass-Luminosity and the Luminosity-...
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2answers
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How could 'rest mass' and 'invariant mass' be the same?

The terms rest mass and invariant mass are often interchanged, however i cannot reconcile these concepts: Consider a photon ...
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0answers
52 views

How Supersymmetry solves the hierarchy problem

The fermion contribution to the Higgs mass is $$\Delta m^2_{H}=-\frac{|\lambda_{f}|^2}{8\pi^2}\Lambda^2_{UV}+\dots$$ And the scalar contribution is: $$\Delta m^2_{H}=\frac{\lambda_{s}}{16\pi^2}\...
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3answers
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On existence of mass in different form [closed]

(I'm a mathematician actually. This is my first question on this site. So please go easy on me if it's a trivial matter or mistake) Lately I've been thinking about special relativity. The thought ...
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2answers
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Centre of mass of solid hemisphere [closed]

I am trying to find the centre of mass of a solid hemisphere using theta as a variable. But I am getting the wrong answer. Can you please tell me where I am wrong. My working is shown in the image ...
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1answer
60 views

How to calculate speed of shrapnel based on explosive's speed of detonation?

I'm trying to calculate the initial speed of shrapnel from a grenade. Using the US's M67 hand grenade as a baseline/reference: Total mass: 400g Explosive's mass: 180g Explosive's detonation speed: ...
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1answer
49 views

From volume density to surface density

Let us say we have a volume $V$ having a volumetric mass(charge) density $\rho(x,y,z)$. Suppose we have a smooth surface $S$ within the volume with a surface mass(charge) density $\sigma(x,y,z)$, if ...
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2answers
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In the derivation of centre of mass, what is the basis of assumption a point having same acceleration as the body?

In the derivation of centre of mass, we assume that a point $X$ exists such that its acceleration is the same as acceleration of the whole body. And as the derivation proceeds, this point comes out to ...
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3answers
130 views

What justifies the use of centre of mass?

Centre of mass gives the location where the 'weighted average' of all the elemental mass of a body acts. Considering that weighted average is one of the many statistical tools used to find the spread ...
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1answer
59 views

Energy and momentum

Does a muon or an electron with the same energy have the higher momentum? According to $E^2=m^2+p^2$ if you increase the restmass, the momentum must decrease. But if we look at a nonrelativistic case:...
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2answers
67 views

How does a quasar convert mass to energy?

I'm trying to understand where the energy for a quasar comes from and specifically if it comes from converting mass to energy. I know that as matter falls into a black hole gravitational energy is ...
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0answers
50 views

The change in mass of a black hole do to Hawking Radiation

Hawking radiation which is the result of virtual particles, which are always created in pairs,(particle/antiparticle) near enough to the event horizon of a black hole, that one of the pair falls in ...
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1answer
46 views

Does the electric field of a charged particle really contribute to its mass? [duplicate]

An electron at rest creates a static distribution of an electric field around it. Wherever the particle moves, it carries or drags the field with itself. Does this electric field contribute to the ...
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1answer
93 views

Greatest relativistc mass possible for a single photon [closed]

I have been told that photons can not be blue shifted to the point where they become black holes, although a photon with a Planck scale wavelength would also have a relativistic mass equal to a black ...
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2answers
61 views

Centre of mass of a solid cone using a symmetrical method [duplicate]

When we rotate a right angled triangle about its perpendicular we get a solid cone. For a right-angled triangle the centre of mass is at its centroid i.e., at $(\frac h3, \frac b3)$. If we consider a ...
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1answer
93 views

How can light reach its speed? [duplicate]

The mass of a photon is said to be 0, But light (photons) get attracted due to gravity of a black hole, that means photons have a mass which is very very very small. And we know that any object with ...
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0answers
22 views

Finding an equivalent shape for a given mass and 3 mass moments of inertia

So I apologize if this is just impossible, but I was wondering if there was a way to find say, the dimensions of a box of a given density that would have the same mass and moments of inertia of ...
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2answers
96 views

What is the mass of photon? [duplicate]

I'm sorry if this question is asked before, but I searched through the site and none satisfied me. In most of the books I've come across, they just write "rest mass of photon is zero." But never talk ...
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1answer
47 views

Derivation using reduced mass for electron orbitals in the Bohr model [duplicate]

Recently in my class, we used the Bohr model to consider the motion of the nucleus about the center of mass of the electron-nucleus system. I understand that this also happens in the Earth-moon system,...
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1answer
112 views

Mass of the fields in quantum field theory

I understand that if I have an action $$S=\int \phi(\Box + m^2 )\phi$$ Then the field $\phi$ has mass $m$ since this is the pole of the propagator of $\phi$. Now If I have an action $$S=\int \phi_1 \...