# 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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### If negative mass should exist, how would conservation of momentum work?

Imagine that a particle with negative mass has been discovered. It is known to obey both the equivalence principle and Newton's second law. This means that the particle is a subject to repulsive ...
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### Is there a mass spectrometer software that can measure the mass of a hydrogen atom [duplicate]

For a school project I need to measure the mass of a hydrogen atom either as a lab experiment or with a computer simulation. Since I don't have the appropriate equipment for the experiment, does ...
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### Does a field gain energy or does the mass/charge?

My textbook reads that when a mass/ charge is moved into the influence of a gravitational/ electric field the field gains/ loses energy rather than the mass/ charge. How can this be explained?
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### A fundamental question about charge and speed of a particle [duplicate]

Hi everybody and happy 2019. In my teaching sessions sometimes someone asks questions i cannot truly answer (although i have many arguments on it) and here's one that really puzzles me: A massless (...
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### What's the mass of $D_1(2430)^{\pm}$?

What's the mass of $D_1(2430)^{\pm}$? The standard reference http://pdglive.lbl.gov/ParticleGroup.action?init=0&node=MXXX035 only shows the data for $D_1(2430)^0$ but not for $D_1(2430)^{\pm}$. ...
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### Is there a mass spectrometer software that can measure the mass of a proton

I spent a lot of hours looking for mass spectrometer software (or Cathode-ray simulator) that can measure the mass of a proton or any sub atomic particle. Until now I only found software that work on ...
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### How much does $b_1^-$ meson's mass differ from that of $b_1^0$?

How much does $b_1^-$ meson's mass differ from that of $b_1^0$? From reading http://pdglive.lbl.gov/Particle.action?node=M011, it is not very clear.
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### Why is neutron slightly heavier than the proton? [duplicate]

With latest knowledge of QCD, is there any explanation for why the neutron is slightly heavier than the proton? Can it be boiled down to a simple formula?
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### Does mass slow down an object falling through the atmosphere? [duplicate]

If I throw two objects with the exact same shape and size, but one of them is heavier, will they arrive at the same time? We learn in basic Newtonian physics that mass doesn't influence the speed in ...
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### What's the difference between gravitational attraction and weight? [duplicate]

What exactly is gravitational attraction? In my textbook it was quoted " all objects both tiny and large objects are attracted to the earth. This is known as gravitational attraction, or the force due ...
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### Can mass still be observed in our universe after moving from a black-hole to a white-hole?

This question is based on the recent papers on LQG black-holes by Abhay Ashtekar. Quantum extension of the Kruskal spacetime and Quantum Transfiguration by Kruskal Black Holes When mass moves from ...
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### Natural and Driving Frequency of a Spring-Mass System

Does $$f = \frac{1}{2\pi}\sqrt{\frac{k}{m}}$$ measure the natural frequency or driving frequency of a spring-mass system? I can't find any resources which confirm this! I believe it measures the ...
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### Which weighs more in atmosphere, $1\,{\rm kg}$ of steel or $1\,{\rm kg}$ of feathers?

I'm having a discussion at the moment regarding the mass of $1\,{\rm kg}$ of feathers and $1\,{\rm kg}$ of steel. The person I'm arguing with states that $1\,{\rm kg}$ of feathers will be lighter ...
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### Scaling of mass density

Let distances scale as $L'=kL$, $k$ is the scaling factor. Then spherical volume will scale as $V'=k^3 V$. Say, the sphere is filled with mass with constant density. If we scale the model with ...
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### Farnes, cosmology involving negative mass

I came across a paper recently which seems to be getting a lot of popular press, and a student also emailed me to ask about it: -- Farnes, "A Unifying Theory of Dark Energy and Dark Matter: Negative ...
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### Where do gravitational waves and general relativity coincide? [closed]

In the first ten seconds of this video (https://www.youtube.com/watch?v=iphcyNWFD10) the host says that gravitational waves were the result of two black holes merging. That would seem like there is ...
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### Couldn't we always redefine units so that inertial mass and gravitational mass are equal?

It is a known fact that inertial and gravitational masses are the same thing, and therefore are numerically equal. This is not an obvious thing, since there are even experiments trying to find a ...
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### Why we can know what flavor the neutrino is created but not their mass? [duplicate]

All neutrino knows which of the 3 flavours they must be upon their creation, however their mass becomes uncertain... why is that? isn't mass supposed to tie to which ever flavours like for example an ...
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### Do vibrations increase an object's mass or weight?

does a vibrating object recieve an increase of mass or weight? and if it does, at what frequency or intensity does it need to vibrate at, and what is the rate of increase? is there a formula for it? ...
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### Mass versus rotation Curves

Is there an equation that describes the relationship between the mass of the Galaxy and rotation curve? I found V versus R graphs and equations that describe their relationship (kind of). But I ...
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### Do the weights of two liquids not add when mixed?

I was given an interesting dilemma today. A co-worker saw me adding a liquid (Diisopropyl ethylamine AKA DIPEA) to a flask filled with another liquid (Tetrahydrofuran AKA THF). I needed to weigh out ...
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### Can we weight dark matter?

We can observe the effect of light as it gets bended in the presence of dark matter, and I wonder how is it possible to measure their mass given that we can't see them and they don't interact with ...
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### Is the barycenter always at the same position?

I am currently preoccupied with the Two Body Problem and I was wondering whether the barycenter, or center of mass, is a static point or if it is moving, and how to calculate its position.
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### Relativistic Mass when Viewed from Different Frames of Reference

I understand relativistic mass and the equations underpinning it. My question deals with how to calculate relativistic mass when an object is viewed from different frames of reference. Consider a ...
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### Work-Energy Theorem for Non-Constant Mass

"The net work done on an object is equal to its change in kinetic energy." Let's say that a rocket is moving upwards while expelling gas and is thus losing mass. (Non-constant mass) As the object ...
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### What is the physical meaning of the trace-free part of the second fundamental form?

Given a submanifold $X$, the second fundamental form tells you about how the submanifold is embedded in the ambient space (intuitively by measuring how a normal vector field varies from point to point....
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### How are these two definitions of energy related/derive from each other? [closed]

How are these two definitions of energy related/derive from each other: $$E = \frac{mc^2} {\sqrt{(1 - v^2/c^2)}}$$ vs. $$E = \sqrt{m^2c^4 + p^2c^2}~?$$ Both equations express the relation between ...
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### What is meant in mass' definition 'resistance to acceleration'? [closed]

Wikipedia: Mass is both a property of a physical body and a measure of its resistance to acceleration What does this mean? I know of the $E=mc^2$ formula. I think, the energy required to '...
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### Why are the volumes above and below the center of mass of a uniform cone not the same?

So today in my physics class we derived the center of mass of a uniform cone, and it all made sense, but near the end of class a student asked, "If you were to split an object into two parts with ...
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### What is more massive, Proton, standard Hydrogen?

If you consider the classical states of hydrogen, one in which the electron is rotating at an orbital distance of $r$ and then take $\lim_{r\to\infty}$ one obtains that the $r_\infty$ state has more ...
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### see-saw centre of mass but with upward forces

Am trying to find how far the centre of mass is skewed from the central distance point. The part I'm unable to grasp here is that I'm working with forces which also push the see-saw upwards (anti-...
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### Can the mass of a hydrogen atom be calculated in a gauge-invariant way?

Please excuse the lengthy question. It involves an interesting controversy which has arisen in discussions on this site: Energy/mass of Quantum Vacuum Relative potential energy vs Absolute potential ...
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### Is the relativistic increase in (relativistic) mass same for a freely falling body as compared to body which is accelerated to the same velocity?

For a similar mass either falling toward a black hole or accelerated by a force is there a comparable increase in mass for similar velocity? Suppose a mass of one kilogram is accelerated to 99% of the ...
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### Does the death of Kilogram ($kg$) affect us in any means in our day to day life? [closed]

Recently, the sleek cylinder of platinum-iridium metal has been discarded and the kilogram is set to be redefined along with ampere for electricity and Kelvin for temperature. Hereafter the Kilogram ...
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### Why the photon doesn't acquire mass with the Higgs mechanism?

I did the computation that from $$(0,v)^{T}(\partial_\mu+igA_\mu^a\tau^a+i\frac{g'}{2}B_\mu)(\partial_\mu-igA_\mu^b\tau^b-i\frac{g'}{2}B_\mu)(0,v)$$ with $(0,v)$ being the expectation value of the ...
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### How does inertia work at the particle level?

I've read recently that the mass of a proton is mostly not given by the Higgs mechanism. But rather it's given by the energy of quarks moving around inside the proton and gluons and other internal ...
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### D'Alembert's principle when the mass of the particles are changing

In the book of Classical Mechanics by Goldstein, at page 19, while deriving D'Alembert's principle, the author assumes that $$\dot p = m \ddot r.$$ However, when the mass of the bodies also changes, ...
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