New answers tagged mass
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Why is the moment of inertia the rotational analog for mass and not inertia?
There are two aspects of mass. One is inertia, defined by Newton's second law, F=ma. The other is gravitational mass, defined by Newton's law of gravity, F=Gm1m2/r2. They are the same in relativity, ...
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Why is the moment of inertia the rotational analog for mass and not inertia?
The equation for linear momentum is $m \times v$.
THe equation for angular momentum is $i \times \omega$.
Notice the similarity between the two form. The measure of the inertia in the linear case is ...
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Why is the moment of inertia the rotational analog for mass and not inertia?
but in my textbook the definitions of inertia and moment of inertia
are very close to one another
They are. The term "moment" is synonymous with the term "torque" which is is ...
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$\phi^4$ quantum fields theory with vanishing physical mass
Assume spacetime dimension $2 \leq d \leq 4$. The $\phi^4$ coupling constant $\lambda$ has mass dimension $[\lambda] = 4-d$. The one-loop mass correction is linear in $\lambda$. Given the UV cutoff ...
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QFT with massless particles
When textbooks specifically mention massless particles, they always mean renormalized mass. Unless protected by some type of symmetry, if the bare mass vanishes, the renormalized mass does not (due to ...
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What would happen to the moon's orbit if we reduce (instantaneously) its mass?
I will assume moon's orbit around the earth is modelled as a Kepler problem. The moon's mass $m_m$ is about 80 times smaller than earth's mass $M_e$. But if you don't neglect it completely, reducing ...
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What would happen to the moon's orbit if we reduce (instantaneously) its mass?
Mass is a conserved quantity. Having it simply disappear violates the known laws of physics. Once you have violated the laws of physics you can no longer ask what the laws of physics predict, since ...
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Accepted
Massless String Having Different Tensions
The reason that an isolated massless string cannot have a net force on it is that if there was a net force the string would suffer an infinite acceleration.
System: string and pulley
In the case you ...
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Massless String Having Different Tensions
We often assume the tension in a string, particularly a massless string, is the same throughout but we have to be careful that we are considering one string, not two. If you think of the classic toy ...
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Is a photon truly massless?
Mass is not an inherent property of energy. It is a property energy can have, but does not always have. Specially, confined energy has associated mass, while free energy does not. A freely traveling ...
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Is a photon truly massless?
I like pictures, and the relevant picture is:
You can ignore the formulae, they are just high school trig, tho, so nothing prohibitive. (The do look bad, though, I think it's because they are crammed ...
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Is a photon truly massless?
Although everyone has heard of the famous equation:
$$ E = mc^2 \tag{1} $$
few realise that this is a special case and applies only in limited circumstances. Specifically it applies only to a massive ...
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Is a photon truly massless?
The correct version of your syllogism is:
$E=mc^2$ for a particle at rest.
For a photon, $E>0$.
For a photon, $m=0$.
The correct conclusion is that a photon can never be at rest.
- 15.9k
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Is a photon truly massless?
Light has inertia: it takes a force to change the direction in which they travel, and if you have a box with light bouncing around inside of it, it takes more force to change the speed of the box than ...
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Are we certain of the mass we calculate for supermassive black holes?
It's a question of magnitudes. The density of dark matter required to explain the rotation curves of a galaxy is far too low to make a significant contribution to the mass pulling on stars and gas ...
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Problem with equation of thrust in a system of variable mass
... whose mass is m referring to?
$m$ is the initial mass of the rocket-fuel system. It is thus a constant. As the rocket propels, its mass is reduced to $m - dm$, where $dm$ is the mass of the fuel ...
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How did Einstein figure out mass (and hence energy) bends spacetime?
One justification for the curvature of spacetime comes from the Ehrenfest paradox. Although I'm not sure of its historical significance.
The circumference of a rotating disk is less than that of a ...
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Accepted
How did Einstein figure out mass (and hence energy) bends spacetime?
I found this explanation interesting.
Why can't I do this to get infinite energy?
Light doesn't lose any energy in constant space-time while leaving earth (or in Newton's world, light speed should ...
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Are there any well-known theories successfully unifying the inertial and gravitational mass?
You have to consider that both inertial and gravitational mass are the same because you are assuming that the body or the particle is going to behave under the accelerating process in the exact same ...
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Why do objects with greater length feel heavier - and how to calculate perceived weight?
I expect a long hose is harder to drag because most of the length is pressing on the concrete. There is a lot of friction.
You could pick up a shorter object, eliminating the friction.
@Paulina mostly ...
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Accepted
Why do objects with greater length feel heavier - and how to calculate perceived weight?
There is indeed an accurate way to calculate the amount of what you call "effort". In physics, this concept is known as work $W$, and is the energy transferred to an object by letting a ...
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How did Einstein figure out mass (and hence energy) bends spacetime?
Here is a modern translation of Einsteins' paper on general relativity.
http://eotvos.dm.unipi.it/documents/EinsteinPapers/Einstein1911English.pdf
The theory of relativity shows that the inertial ...
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