# Tagged Questions

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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### gravity cancelling dark energy

Say there were 2 objects with certain masses (e.g. $m_1$ and $m_2$). If they were close together gravity would attract the 2 objects. If they were a large distance apart the expansion of the universe (...
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### Rest mass energy of electron

For electron's energy why we some time use the word "REST MASS ENERGY" why we use this word as electron is always spinning?
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### Zero $g$ in a black hole?

At the very centre of the Earth, masses cancel each other out, creating an effective zero-$g$ environment. Would the same happen in a black hole?
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### Period of mass in circular motion [closed]

I've been trying for 4 days now to solve my physics lab assignment but now I'm starting to think there must be a mistake in the question. You know those rotating mass experiments where you have a mass ...
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### Is photon massless? [duplicate]

if photon is massless then in E2=m2c4+p2c2 is m=0 ? and p=mv1-mv2 shouldnt be zero too. if both the statements are true then does photon has no energy?
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### 3D donuts and the centre of a black hole [closed]

I have been trying to imagine ways to visualise the gravitational field of the earth... It's near zero at the outer edges of the atmosphere, strong at sea level, strongest at the quarter point, then ...
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### Does it take a larger force to stop a faster object?

Does it take a larger force to stop a car that is moving at a velocity 2*v than if it is moving at a velocity v? I'm confused as the force required to decelerate a car depends on the mass and the ...
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### Effective mass of two objects

I read that if we want to perform conservation of energy taking one object as frame of reference, we need to assume that the other object has the effective mass and velocity. And effective mass is ...
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### How can neutrinos oscillate though the lepton flavors have differing masses?

Since the total mass-energy for the neutrino presumably does not change when a neutrino changes lepton flavor, though the mass is different, what compensates for the gain or loss of mass? Does the ...
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### What is the gravitational pull if one has as much mass above them as below them? [duplicate]

I understand the previous responses to other answering if you were at the center of a planet, would you be weightless? Yes you would due to the forces of gravity pulling at you from all sides. ...
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### What is $r$ in angular momentum quantization rule?

We know $$mvr= nh/2π$$ What is $r$ here if I consider positronium system. I suppose it should be the radius of the orbit in which both are moving. But when I take the above equation and electrostatic ...
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### How to calculate relativistic mass versus time?

I know that relativistic mass is calculated as: But when mass m0 gets bigger, also mass of the accelerating body mass m gets bigger so m0 gets bigger and so on. So if body accelerates with ...
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### Double the mass in the universe, double the inertia

If I double (halve) the mass in the visible universe, will my inertia double (halve)? I think it should, at least as soon ''I have received the news of this doubling''. But what does the General ...
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### Remotely finding the mass of a satellite

I have a question similar to one I've asked earlier (Calculating mass of an orbiting body with force and acceleration), but without a specific formula... How can you find the mass of a satellite body ...
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### Calculating mass of an orbiting body with force and acceleration

I'm new to physics, and it's a lot to take in- but there is a problem that I really can't seem to wrap my head around- finding the mass of an orbiting body, like an asteroid. I've looked around a lot ...
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### Is there a connection between gluons and photons?

I was wondering if there is any sort of connection between a gluon and a photon since they are both considered massless.
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### If there is no gravity, does that mean there's no mass as well? [duplicate]

I have demonstrated that weight only is measured based on the gravitational pull of where you live. For example, the gravity on the surface of Mars is three times smaller than the gravity on the ...
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### Why does a teeter-totter (see-saw) tend to incline towards the heavier end?

Why does a teeter-totter (see-saw) tend to incline towards the heavier end? Since objects of different mass tend to fall at the same speed (assuming a vacuum), why do then heavier objects push harder ...
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### Negative Mass Square

I'm reading a book about neutrino physics (from 1997). In the chapter about neutrino mass they list results of certain experiments. All of them get a negative value for $m(\nu_e)^2$ but a positive one ...
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### Constructing a Hamiltonian from a mass matrix?

I was solving some questions regarding the Hamiltonian, which required a lot of algebra, but as I finished and looked professor answer I saw that he constructed a matrix from the kinetic energy and ...
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### Does a toy top weigh less when it is spinning?

I am under the understanding that a toy top will weigh less when it is spinning. The Russians made a spinning type transport back in the 70s to lessen its payload over the tundra. Is this an effective ...
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### What is the mass of a wave?

The slide called "QUANTA" here says that "One Quantum has a definite mass" and the picture shows a wave. So, What is meant by the mass of a wave?
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For my own knowledge and to understand why. I am trying to convince myself that the center of mass for a rigid solid sphere is at the origin (0,0,0). I begin with the basic definition of CM $$\... 3answers 2k views ### What defines the mass of elementary particle? The electron is particle. The mass of electron is 9.10938215(45)\times 10^{−31}\, {\rm kg}. But why is the mass exactly what it is? What in physics defines the mass of elementary particle? 1answer 70 views ### Mass - Unification of kinetic and gravitational mass definitions As a kinetic definition, mass of a body is a measure of the translational inertia of the body. There is also the gravitational definition of mass. Can these definitions (kinetic and gravitational) be ... 1answer 46 views ### How to derive an equation for the mass of a pendulum bob? How to derive an equation for the mass of a pendulum bob? If anyone knows of a resource that shows this (I've looked) or could explain how to derive an equation for the mass of a pendulum would be ... 2answers 1k views ### If quarks didn't have mass, could protons (and neutrons) exist? I read here (mass of a proton) that the mass of a proton is mostly (99%) due to the energy of the strong nuclear force which binds the quarks together, and not the actual mass of the quarks. My ... 0answers 43 views ### Point of zero gravity for fixed masses? Given a number of fixed point masses in 3D space, is there necessarily one or more points where there is zero gravity (ie, the combined gravity of the masses cancels out), and, if so, how do I find ... 0answers 34 views ### Charged Universe and charge-dependent inertia/anti-inertia I posted this same question as a follow up for the main question here. I expected to get a quick answer but since none have come up I raise it as a topic in its own right. So the question is: Suppose ... 1answer 229 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 ... 3answers 1k views ### Why do non-accelerating objects exert force on each other? The equation for force is \vec{F} = m\vec{a}, where \vec{a} is acceleration. Acceleration is a change in velocity. However, if an object with constant velocity (i.e. 0 acceleration) hits another ... 1answer 63 views ### Can 3 objects be collinear? Suppose there are 3 objects floating in some space, without anything else besides this 3 objects. Is there any way for them to end up collinear at any given moment (assuming they start at completely ... 2answers 55 views ### Acceleration due to gravitational force [duplicate] I need some help with below. So according to Newton's 2nd law, a=F/m, for a given mass, the acceleration depends on mass. But acceleration due to gravity is independent of mass. There seems some ... 2answers 46 views ### A drop falling in the condensed air A drop is falling in humid air with air resistance equal F_r = - \alpha v^2. In t = 0 the drop is ideally spherical, h above the ground, has mass m_0 and velocity v_0 = 0. What mass and ... 1answer 41 views ### Kinetic energy during 1 minute - wrong? [closed] I've come across this IEEE paper whilst researching for a project I've undertaken regarding a bicycle generator. This paper concerns an exercise bike powered electric generator. Essentially they have ... 1answer 192 views ### In which experiments the charge to mass ratio of proton was determined? Are there experiments where the charge to mass ratio for protons have been determined in the same way as in Thompson’s experiments (where he determined the charge to mass ratio of electron) but with ... 0answers 85 views ### Does adding static charge to a body increase its mass? If a body becomes charged by losing electrons for example, it will experience a braking force when it is accelerated due to radiation called Bremsstrahlung radiation. Part of the energy used to ... 2answers 1k views ### Which is the lightest thing in this universe? Is that a photon or neutrino? I hear a lot of people saying that neutrino is the lightest subatomic particle but according to me a photon must be the lightest as nothing can travel faster than light because it gets heavier and ... 2answers 250 views ### Why isn't a meter defined from a kilogram of water? Why are there different official definitions for a kilogram and for a meter when a meter can be defined by the volume of a kilogram of water? For instance, using the triple point or some other state ... 2answers 63 views ### Weighing a baloon I know of methods of measuring the mass of a gas using chemistry, but this is unrelated. I was wondering if it is possible to deduce the mass of a helium balloon by measuring its mass it on a scale ... 1answer 93 views ### Other values of mass of the electron and the charge of the electron? Are there whatever experimental data other than Millikan Oil Droplet experiments data and Stoney calculations from electrolysis low, or some experimental indications pointed on the possibility that ... 1answer 71 views ### Why can center of mass be used in calculating gravity? Why can gravitational forces be based on the center of mass. Due to the fact that gravity is related to the square of the distance should not the gravitational sum of every particle exceed the force ... 0answers 74 views ### What is the real meaning of mass in quantum mechanics? [duplicate] I know the meaning of mass in classical physics, the ratio of force and acceleration. But what do we mean when we talk about the mass of an electron in quantum mechanics? 4answers 222 views ### Does dark energy work like gravity, but the opposite way? If a body has more mass gravity will exert a greater force on it. Does that apply also to dark energy? In other words, if a body has more mass, will it be affected more by dark energy? (that is, will ... 1answer 65 views ### Question regarding the mass of an alpha particle when travelling at a speed approaching the speed of light [duplicate] The speed of an Alpha particle is: 10^7 m/s. This is a speed approaching the speed of light. hence, should the (relativitic) mass of the Alpha particle vary? 1answer 29 views ### Have hypothetical particles with gravitational mass unequal to their inertial mass been proposed in the past, e.g. as candidates for dark matter? This is a question about history. To my understanding the equivalence of intertial and gravitational mass for all known particles is a weird empirical coincidence that has been confirmed to high ... 3answers 106 views ### How to model vibration damped by applied/contact force? I am computer science student and I am working on a project which needs to know how the vibration of phone is damped by applied force (when human touches the phone). I have read many articles about "... 1answer 128 views ### Why is V=(1/2) m^2 \phi^2 for a free relativistic scalar field of mass m? Bit of a basic question here but how come for a free relativistic scalar field of mass m such as Klein Gordon theory, we take the potential to be$$V=\frac{1}{2} m^2 \phi^2 Is the mass term ...
In QFT we work with Lagrangians which contain terms $m$ such that the relativistic relation $E^2 = p^2 + m^2$ is satisfied. By classical analogy $m$ is called the 'mass'. We note that due to the ...