What is Relativistic mass: Definition and 116 Discussions

The word mass has two meanings in special relativity: invariant mass (also called rest mass) is an invariant quantity which is the same for all observers in all reference frames, while the relativistic mass is dependent on the velocity of the observer. According to the concept of mass–energy equivalence, invariant mass is equivalent to rest energy, while relativistic mass is equivalent to relativistic energy (also called total energy).
The term "relativistic mass" tends not to be used in particle and nuclear physics and is often avoided by writers on special relativity, in favor of referring to the body's relativistic energy. In contrast, "invariant mass" is usually preferred over rest energy. The measurable inertia and the warping of spacetime by a body in a given frame of reference is determined by its relativistic mass, not merely its invariant mass. For example, photons have zero rest mass but contribute to the inertia (and weight in a gravitational field) of any system containing them.

View More On Wikipedia.org
Recent contents Top users
  1. A

    A Question on Relativistic Mass (SR)

    Hello. I am independently studying modern physics. I have a basic special relativity question. Consider a completely inelastic collision Of course, objects are moving at a constant velocity before and after the collision with respect to a stationary observer. Let's call him Rick. Suppose that...
  2. Egregious

    Relativistic Mass thought exercise with approaching bodies

    "Relativistic Mass" thought exercise with approaching bodies I understand that the concept of 'relativistic mass' is somewhat controversial, but for reasons that are unclear to me. Nevertheless, I humbly pose the following thought exercise/inquiry: For starters, I understand the formula for...
  3. T

    Is Light's Mass Infinite at the Speed of Light?

    Hi, a while back i had ran into the equation for dynamic mass [M = m/√(1-(v^2/c^2))] and had immedietly taken an interest in it in that it seems to imply that for an object with mass moving at the speed of light its mass would become, virtually, infinite. Is this an erroneous assumption? If not...
  4. L

    Relativistic mass and work problem

    Homework Statement A body has rest mass of 10^5 Kg. Find how much work must be done on the body to give it a velocity such that the clocks on the body run at 1/10 of the rate of the lab clocks. compare the work energy with the rest energy of the body Homework Equations γ=1/√(1-(v/c)2)...
  5. A

    Relativistic Mass as described by Kenneth Krane in 'Modern Physics'

    Homework Statement Mr. Krane describes this scenario in a presentation of relativistic mass in his book Modern Physics John Wiley & Sons, Inc. 1983 p. 36-37 According to one observer, two balls of equal mass, m1 and m2, are approaching each other at equal speed, v. The proper mass of...
  6. S

    Relativistic mass thought experiment/proof?

    Hey all, After reading some fairly elementary texts on special relativity, I understand length contraction and time dilation no problem, as it is well explained with examples of proofs, but I hate to say that relativistic mass is explained nowhere. I know this question has probably been asked...
  7. M

    Relativistic mass increase appearing to form a black hole vs. a real black hole

    As I understand it, if you are moving fast enough relative to me, your mass increase will cause you to APPEAR like a black hole to me, even though you will not see yourself as a black hole. It would be an illusion, right? And also you would see me as a black hole while I would reject that view...
  8. C

    What is the issue with photon rest mass?

    I read somewhere else on this forum that photons have zero invariant mass, only relativistic mass. Here is my problem, Einstein's equation for relativistic mass says that is invariant mass is zero then so will relativistic mass at all velocities. If a photon does have relativistic mass, then...
  9. zonde

    Relativistic mass of falling body

    Let's say that body with rest mass m0 is falling toward gravitating body from infinity. Near gravitating body it falls with speed v=\sqrt{\frac{2MG}{r}} Is it right that relativistic mass of body falling at speed v near gravitating body is equal to the rest mass of the same body at infinite...
  10. D

    Relativistic Mass vs. Invariant Mass.

    Hey all, I'm quite confused on this and am curious to be put straight. Now I understand the basic principles of relativity, this one just bugs me. Now I have always been taught that the famous E=MC^2 formula was proof that mass would reach toward infinity as it neared the speed of light...
  11. SamRoss

    Derivation of Relativistic Momentum WITHOUT using Relativistic Mass?

    Derivation of Relativistic Momentum WITHOUT using Relativistic Mass? Does anyone know a way to derive relativistic momentum without falling back on the concept of relativistic mass? Also, if it is not already part of the derivation given, does anyone know how to show that relativistic...
  12. C

    Why can't there be a center of relativistic mass?

    As the title. More specifically, with respect to the center of momentum frames massless particles don't have, why not if they still do have relativistic mass? (Bracing for an easy answer to a stupid question...) :redface:
  13. K

    Lorentz ether frame, Relativistic Mass, and Inertia

    It is obvious from particle accelerators that accelerating a mass increases its inertia. That should be a valid observation in all frames. But if the angle between the acceleration vector and the velocity vector is relative to the observer, then whether the mass is accelerating or...
  14. T

    What exactly is relativistic mass?

    And why does it increase as you travel faster and faster?
  15. K

    Why is the relativistic mass a rejected concept?

    http://www.weburbia.com/physics/mass.html If it is not wrong, why not go about setting it straight and making it clear? Are we going to totally ignore the physical implications of having a relativistic mass, such as its dependence on the work done on the body relative to a given inertial...
  16. R

    Calculating relativistic mass of neutrons, wrote out my plan please critique

    Homework Statement I am given an equation, say (239/94)Pu-->(110/53)Fe+(125/41)Nb+4neutrons I am asked to calculate the relativistic energy so I do that. Q=m(left)-m(right)c^2 I know that m(left)=m(Pu) I know that m(right)=m(110Fe)+m(125Nb)+4m(neutron) (i put the answer into MeV for...
  17. T

    Relativistic Mass and high relative Velocity of distant galaxies

    I think I may have asked this before, but I don't think I received a reply that made sense, at least to me. Does the gravitational force between distant galaxies become larger and more significant due to their Relativistic Mass at high relative velocities and especially at luminal and...
  18. SamRoss

    Derivation of Energy-Momentum Relation WITHOUT using relativistic mass?

    Does anyone know of a derivation of the energy-momentum relation that does not make use of relativistic mass? In other words, a derivation that only uses invariant mass.
  19. R

    Solving an ODE Related to Relativistic Mass Change

    Homework Statement \frac{dp}{dt} = \frac{d}{dt}\frac{mv}{\sqrt{1-\frac{v^2}{c^2}}} = F Find v(t) show that v -> c as t -> infinity & find the distance traveled in time t if the object starts from rest. Homework Equations The Attempt at a Solution Ive tried rearranging it into either a...
  20. SamRoss

    Is relativistic mass not an appropriate concept?

    Is relativistic mass not an appropriate concept?
  21. maverick_starstrider

    Relativistic Mass and Electrons vs. Muons

    Hi, I can't say I've really ever done much relativity but this made me wonder. Imagine we have some frame where a muon and an electron are interacting where the electron's energy is so high that its relativistic mass can be said to be HIGHER than that of the muon in the same frame. I...
  22. S

    Relativistic mass and Hubble constant

    Student here, please forgive... I have a question about relativistic mass in galaxies. Is the mass of far away galaxies affected by expansion of universe? That is: Is mass of a far away galaxy is different for observer there compared to the observer here? Let's say there is a galaxy identical...
  23. A

    Relativistic mass affect weight of an object?

    For example, a top spinning near the speed of light, would the relativistic mass be affected by gravity and therefore increase the weight of the object? If it does, then are the highest speeds which we could realistically get it to spin at it not even close to the speed of light, making any...
  24. A

    Planck relation, relativistic doppler effect, and relativistic mass

    I've been trying to graph an idea I had, but frankly I don't understand SR well enough to ensure my assumptions are correct, and that I'm using the correct formulas. I would appreciate any input/corrections you folks could give. Here's the idea, which I'll follow with my assumptions: Idea...
  25. L

    Does relativistic mass induce gravity?

    I've read conflicting accounts on this subject. Some say it does, some say it doesn't, some say the entire idea of relativitic mass is a "rampant pedagogical virus". So please inform me when I'm making a mistake. So does the gravity of an object it exerts on it surroundings increase with it's...
  26. R

    What is relativistic mass and rest mass

    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...
  27. K

    Relativistic mass increase due to high temperatures inside stars?

    Wikipedia says that the core temperature of our Sun is 15.7×10^6 Kelvins. I don't know what that means in terms of protons' velocities inside the core, but I bet they move pretty fast. Could they move that fast that they have a noticeable increase in mass due to their relativistic speed...
  28. O

    Accelerating Universe, Relativistic Mass and Dark Energy

    Hi! Well, I have a problem, I'm writing Extended Project For Applied Science about Death of the Universe, I am stuck. I am really desperate so I decided to put it on forum. First: The Universe is accelerating so, according to Lorentz's Factor, its mass should be increasing m = \gamma m_{0} =...
  29. P

    Is Relativistic Mass Plausible?

    I've read contrasting sources concerning the concept of an object increasing in mass at relativistic velocities. Some of my older calculus texts mention this as being accepted by physicists, while a newer(by comparison) textbook called Principles of Physics: A Calculus-Based Text by Serway and...
  30. W

    Comparing Electron Mass in Different Speeds

    Homework Statement An electron has a rest mass of 9.11 x 10^-31 kg. The speed of the electron in the cathode ray tube of your computer monitor is 4.00 x 10^7 m/s. However, the speed of the electron is 0.98 c in a particle accelerator used in cancer therapy. How many times heavier is the...
  31. U

    Inverse Funcation of Relativistic mass

    The relativistic mass equation shows the relationship between relativistic mass and speed. Basically showing that the closer u get to light speed the less relativistic mass you have, but ur rest mass will be the same. I was asked by my friend what the inverse of that formula means. Thus I...
  32. M

    What is the Relativistic Mass of a Muon?

    Homework Statement A muon traveling with negligible energy loss at v = 0.996c travels past a 4730m mountain. What is the relavitistic mass of the muon given the rest mass energy of 1.69 x 10^-11 joules? Homework Equations The Attempt at a Solution I think I should be using...
  33. R

    Relativistic Mass and Energy Convservation

    Does relativistic energy contribute to gravitational 'pull'? If so, then does the acceleration of a body being 'pulled' by gravity cause it to increase in mass, thus weighing more and accelerating even faster? Does an object have greater mass because it's original mass pulled it toward...
  34. M

    Photon energies relative to movement, and relativistic mass Q's.

    Not sure if this should go here or in the relativity forum... let me know if I need to move it. I was reading something, and it said this: "A photon also has a rest mass, which is zero, even though a photon is always moving at the speed of light, and so is never at rest. But if an observer...
  35. jtbell

    In which areas of physics is relativistic mass used?

    When I was a graduate student in experimental high-energy particle physics c. 1980, none of the people I worked with (fellow experimentalists and theorists alike, in that field) used relativistic mass m = \frac {m_0} {\sqrt {1 - v^2 / c^2}} in their work, to the best of my memory. The only...
  36. J

    Calculating Relativistic Mass of Photon & Electron

    Let me see if I got this right. A photon has no rest mass, and it travels at the speed of light. Knowing the wavelength of the photon will give us the momentum using the De Broglie relation. Now can we say that the momentum of the photon is = relativistic mass of the photon X the speed of light...
  37. rcgldr

    Relativistic Mass: Does it Increase?

    From a thread on GPE: This one has me curious as well. Does mass increase as velocity approaches light speed? Does "weight" also increase? Does the stregth of gravity from the object also increase? If the mass and weight increase by the same ratio, then the rate of acceleration...
  38. F

    Relativistic mass and the speed of light limit

    Is the relativistic mass the reason that objects with mass cannot reach the speed of light? >> The book gave it as the explanation of why objects with mass cannot reach the speed of light. The book says that as the object increases its speed its mass increases making it require more energy to...
  39. C

    Relativistic Mass: Definition & Explanation

    I have just recently began to understand relativity, right now I get time dilation and length contraction but I do not get relativistic mass. The book I am reading does not defy it very well (or perhaps I should read the chapter again) but it gave it as the explanation of why objects with mass...
  40. J

    Inertia and relativistic mass.

    I've seen inertia described in a few ways and it is simply a mass' resistance to acceleration. But inertia in my mind starts to break down in my mind in relativistic terms because of mass-energy equivalence and the speed of light. As mass and inertia are directly related then shouldn't and...
  41. P

    Who coined the term relativistic mass

    Who coined the term "relativistic mass" I asked this question before and never got an answer. I'm hoping that new people are on here who might just know the answer to the question: Who coined the term "relativistic mass" and where, i.e. I need a reference so I can read the source of the terms...
  42. redtree

    Relativistic mass and space-time curvature

    Does relativistic mass curve space-time, i.e., does relativistic mass affect the gravitational field of an object?
  43. G

    Exploring the Paradox of Relativistic Mass Increase

    Hi all - this (seeming) paradox has been brought up on a few other forums with less than illuminating results. I'm curious to see what the solution is. Okay, so, you're watching a massive object approach the speed of light. From your reference frame, you are measuring the increase in apparent...
  44. C

    Q about relativistic mass increase, starship

    A warning is often given that if one wants to have a spaceship traveling at relativistic speeds (usually to get to another star), the ship's mass increases, making acceleration more difficult. But if it where an antimatter propelled ship, with mass being turned into energy, then wouldn't the...
  45. K

    Relativistic Mass: Does Spacetime Distort at High Velocities?

    After reading a lot of posts lately, I believe I recall someone mentioning that physicists no longer look at the relativistic effect of mass-"dialation" but rather velocity. I am not 100% sure I understand this so firstly, please explan a little. The way I understood it was that the more...
  46. N

    Derivation of the Equation for Relativistic Mass

    Throughout pages on the internet I've seen the following relationship between rest mass and relativistic mass: m = \frac{m_0}{\sqrt{1-\frac{v^2}{c^2}}} However, I have been utterly unable to find any sort of derivation or explanation of this formula, other than such explanations as...
  47. L

    Schwarzschild Radii and Relativistic Mass

    Hello, folks - here is a question that I have been pondering for about 20 years. As I understand it, the Schwarzschild radius can be thought of as a measure of how much mass can fit within a given space before that space warps from gravity to such an extent that it acquires an event horizon...
  48. E

    Time in SR and relativistic mass

    Is it possible substitutive explanation of SR: "because of larger relativistic mass everything moves more slowly." I tried to to get this substitution mathematically, but it not works. I know that lorentz contraction should be included as supposition that things work. For instance: a =...
  49. B

    How Is Relativistic Mass Measured Indirectly in Physics?

    Measuring the relativistic mass and energy When we speak about a physical quantity we should define it and it is compulsory to propose a procedure of measuring it. But how does one measure relativistic mass? The answer lies in the fact that relativistic mass (as well as proper...
  50. P

    Objections to Relativistic mass

    Hi folks. I need your help. I'm starting to rewrite my paper on the concept of mass in relativity and I'm trying to compile a list of objections to the concept of relativistic mass. I've managed to compress tghe objections to a list of about 17 items long. If you have any objections you believe...
Back
Top