Rest mass Definition and 103 Threads

My book says that if two objects collide completely inelastically, the rest mass of the composite is greater than the sum. I assume this happens because the objects heat up and this is counted in their energy. However, in other problems the book assumes the rest mass of objects/particles is...

1) How can get work done on a photon because work done = kinetic energy it depends on mass, but the rest mass of a photon is zero 2) From this equation E=PC , does this mean E of a photon is 0 because P must be zero since it depends on mass?

I'm new to physics, so I'm sorry if this is a dumb question. If a string cannot be point like, it has measurable spatial dimensions, then it must have mass. Well if a string was vibrating at the resonant frequency of a photon, and at rest it must have mass and therefore a nonzero rest mass. This...

Calculating the rest mass of Ra [simple!] Homework Statement Calculate the rest mass of 226/88 Ra.Homework Equations The Attempt at a Solution There are 88 protons and 138 neutrons. Therefore, (88*1.007276)+(138*1.008665)=227.8361u But the answer says 226.0254u. It also says 4/2 He is 4.0026u...

Penrose says in “Cycles of Time” that rest mass isn't exactly a Casimir operator of the de Sitter group, so a very slow decay of rest mass isn't out of the question in our universe. If rest mass is strictly conserved, should it be a Casimir operator of the de Sitter group? Decay of rest...

If the universe were expanding very, very rapidly, would rest mass disappear? I've been reading "Cycles of Time" by Roger Penrose, which is about his "conformal cyclic cosmology" theory. The gist of it is that in the VERY VERY distant future, like a googol of years from now, when all the...

hey guys ...i've got a doubt.. when there is no absolute rest in the universe...how is rest mass defined?

From my understanding E=mc2 shows that relativistic mass is equivilent to energy. And hence the conservation of relativistic mass is a restatement of the conservation of energy. Also from my understanding it also indicates that rest mass can be converted into photons. Also I think this...

Einstein's theory of relativity is based on the fact that all motion is relative, which precludes the existence of a universally defined state of rest (priviledged reference frame). Einstein also recognises the existence of rest mass. If an object were at its rest mass, wouldn't it be perfectly...

Does proton diameter increase with the addition of energy, such as thermal energy? I guess this is also to ask if a particle's rest mass can increase. And, if a proton can gain rest mass, does the diameter correlate with it?

I haven't used the template because I just need some reassurance on understanding a topic, not help with a question! When two particles annihilate (e.g. proton and antiproton), the resulting radiation will have a minimum energy of the sum of the rest mass energies of the two particles, right...

Rest mass ? What on Earth ?! I have a data table given to me by my examining body and it lists the REST mass of a proton and the REST mass of an electron along with their values. My question is why do they specify the REST mass ? Does the mass of either sub atomic particles change when they...

Consider the following situation. Two particles are initially separated by some distance and are then pulled further apart, thus increasing the potential energy of the system (due to the gravitational force of attraction between them). If I am correct in understanding special relativity, then...

Hi All, According to the basic notions of Relativity, in the reference frame, in which a certain body is at rest, we are allowed to measure the rest mass of this body. Nevertheless, we know from thermodynamics that at temperature T there is a certain amount of disordered microscopic movement...

Is rest mass just an illusion? In Proton, for example, most of the rest mass is relativistic mass of quarks, moving at relativistic speeds. Quarks are quite light, but if we go deeper, the rest mass of quark is also an illusion - all particles have rest mass = 0, and what we call mass is...

what is "relativistic mass" and "rest mass".. as far as i know the rest mass is the mass which measured by an observer who is at rest relative to the object (please correct me if this is not right), if this is right... what if when the object is traveling at the exactly same velocity of the...

Is there actually a superfluous reason for rest mass. I only ask because clearly as far as I know, all particles have spin, and I am led, (possibly falsly) to assume that so do things such as photons (although we know photons don't have rest mass anyway). Thus if "everything" has spin, (lets...

Is there a direct relation between the relativistic mass (total energy) and rest mass? In other words, can we say a proton has higher rest mass than an electron because a proton-antiproton annihilation would produce that much more energy than electron-positron one? And the ratio of energy...

Hi guys, simple question I have: Do particles without a rest mass (including EM radiation) cause spacetime to bend? Or only those with a rest mass have gravity?

Homework Statement Calculate the rest mass of Deuterium nucleus. Homework Equations Is it correct to calculate its mass using hydrogen? i.e. 2*rest mass of hydrogen?.. The Attempt at a Solution As stated in textbook, the rest mass of deuterium = 3.34330*10^-27 kg If it is...

From my reading i am seeing the answer But according to special relativity, light ALWAYS travels with the light speed c, and is NEVER at rest and from this statement i am supposed to gather there is no rest mass. But logic tells me just because light is never at rest, doesn't necessarily...

According to my physics textbook, the equation E^2=\left(mc^2\right)^2+\left(pc\right)^2 suggests that a particle may have energy and momentum even when it has no rest mass, and that the total energy then is E=pc. This strikes me as odd, since the relativistic momentum of a particle is given by...

Homework Statement What is the rest mass energy of one mole of neutrons? Hint one mole is 6.02 x 1023 particles (avocado's number), and the neutron has mass m=1.675 x 10 -27 kg. Homework Equations The Attempt at a Solution I wasn't sure of the relationship between moles and...

Hello all, First off, I am not sure if these questions belong in this category. For a couple of years now I have been interested in physics/quantum mechanics, and a while ago I decided it was probably my main interest. After realizing my school did not offer physics, and therefore not...

Suppose we have a box at rest that is filled with a uniform gas. We denote the volume by V and the pressure by p. Suppose next that we apply a small force to the box and accelerate it until it has a speed v. The key question is: Is it harder to accelerate the gas because it takes work not only...

In the article "Why does light have invarient speed?" on PF (first URL in attached file), there is a statement that for photons, m_0 = m \sqrt{1 - \frac{v^2}{c^2}} is 0 since v = c. (I'm not sure if the author is stating this or quoting somebody else.) Is this a valid...

I am looking for an expression for the total energy of a particle of rest mass m_0 that includes kinetic and gravitational potential, if there is such a thing. If I take the product of the time-components of the four-velocity and four-momentum vectors, I get m_0 c^2 \gamma^2 where...

I understand photons have no rest mass, but I also learned in my physics class p=h/(lambda), and that mass depends on the frequency, my question is why can't something moving at c have rest mass if it can have... momentum I suppose is the term...

Theoretically, if an object were to have negative rest mass, would it travel faster than light?

Hello, I'm working on this problem and I'd like to know how to find the invariant mass using just the lab-frame momentum and rest mass. I've found a lot of equations that deal with E, and I'm not completely sure what that is either. Thanks

Suppose the neutron decay time n was 89 sec. AND the difference in rest mass between neutron to proton, Qn, was 0.129 MeV. What would the maximum Helium fraction, Yp, be?

How can cosmology set an upper limit on the rest mass of neutrinos if we know that the universe contains about 450 neutrinos per cubic centimeter?

If we can't find a frame of total rest, how can we calculate a rest mass?

What is the rest mass m of a particle traveling with the speed of light in the laboratory frame? i believe m = (E² - (pc)²)^.5 / c² is the correct equation to use? as velocity goes up, so does energy and momentum? so when velocity is at speed of light, E = infinity and momentum = infinity...

The mass of sun is determined by measuring the distance of a planet from the sun,the speed of that planet around the sun ,and then using Newtons law of gravity.In the same fashion one can determine the distribution of mass in a galaxy by observing the position adn motion of the stars in that...

ABSTRACT In this paper we will present the mechanical dynamics of a gravitational system resulting from a specific, rest mass, scalar potential relation, that is equivalent in predicting orbital and photon motion to that of General Relativity in the weak field solutions. The weak solutions of...

A particle of rest mass m. and kinetic energy 2m.c^2 strikes and sticks to a stationary particle of rest mass 2m.. Find the rest mass M. of the composite particle. (.=zero subscript) The answer is (17)^1/2(m.)

charge is quantized. what about rest mass? do particles of the standard model have rest mass that is quantized, and comes in quantas of mass, with i imagine the electron being the lowest that have rest mass (the neutrino does not appearl to have a rest mass) do particles of the standard...

do particles of the standard model have rest mass that is quantized, and comes in quantas of mass, with i imagine the electron being the lowest that have rest mass (the neutrino does not appearl to have a rest mass) ? please move to other more appropriate forum

Why is the relation between an electrons rest mass inversely proportional to its distance from the nucleus (sp)? Thanks, -scott

The excited K* meson has a rest mass of 1.5828E-27 kg/ a What is the rest amss energy in joules? 1.43E-10 b What is this energy in MeVs? 893.75 here's where i need help c Now these K* are accelerated to a speed of 2.97E8 m/sec. What is the relatavistic mass of these K* in kg and MeV/c...

How does E = mc^2 imply that no object with rest mass can ever reach the speed of light?

I'm still very confused to some extent. I know that from QM, an electron, due to Heisenbergs UP can't be measured definitely. It is following Schrödingers equation, and is presented as a vector in Hilbert space ,i.e. in a "electron cloud" of propability. But here my theory is incomplete...

relativistic mass is defined by the lorentz contraction equations (i.e time & legnth). but why should mass increase only for speeds very close to c? is there any theory that explains this? we know that rest mass is basically the resistance to acceleration and the higgs theory postulates...

what is rest mass? why does a photon have rest mass zero? :rolleyes:

a moving particle has a rest mass which is double its kinetic energy. Find its speed and momentum..=)

Hi, got an exam tomorrow for particle physics and need a question answered concerning helicity. How would it be possible to determine if a photon had a non-zero rest mass, based on measured helicity values? Thanks Ray

If it's energy, a photon must curve space. If it's rest mass a photon doesn't curve space and an object going at speed 0.99c doesn't curve space more than when it's not moving. A friend of mine asked me this question after asking two of his profs at McGill University and getting two...

Are Higgs particles all the same mass? Does a proton have more Higgs particles associated with its rest mass than an electron has associated with its rest mass? And does the mass of all Higgs particles equal the total rest mass of the universe? Do Higgs particles have short lifetimes like...

Back in 1960's ,one could frequently hear opinions/claims that neutrino rest mass is 0.Not a very small one ,but exactly=0.Therefore,a nutrino would just like photons propagate at light velocity through the space. What has changed in a meantime (since decade -two), except better insight to...