# What is Gravitational mass: Definition and 44 Discussions

Mass is both a property of a physical body and a measure of its resistance to acceleration (rate of change of velocity with respect to time) when a net force is applied. An object's mass also determines the strength of its gravitational attraction to other bodies.
The SI base unit of mass is the kilogram (kg). In physics, mass is not the same as weight, even though mass is often determined by measuring the object's weight using a spring scale, rather than balance scale comparing it directly with known masses. An object on the Moon would weigh less than it does on Earth because of the lower gravity, but it would still have the same mass. This is because weight is a force, while mass is the property that (along with gravity) determines the strength of this force.

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1. ### B Some doubts from Carroll book

I'm reading Carroll's GR book. I'm able to follow the introduction so far, but a couple of paragraphs are a bit hard to decipher: What exactly does "couples to" mean? Right now that's just a vague phrase to me that implies gravitational field has something to do with EM - but what's the...
2. ### I Time dilation from galactic gravitational mass

I've been thinking about how rotational speeds don't fall off high distances from galactic centers, for which dark matter is generally an explanation for the increase in acceleration Speed = distance / time But time is relative What "time" is used in these calculations? Wouldn't time be...
3. ### B Tangran, Inertial Mass and Gravitational Mass

Imagine a tangran puzzle, in which an extra piece "y", identical to piece 'x', is maliciously added. No matter how hard the player tries, he will never be able to restore the game's original form, that is: a perfect square. This illustration has a clear purpose: If gravitational mass and...
4. ### B Gravitational Mass of C/2 Objects: Jim Adrian's Inquiry

I would like to be sure that objects passing at high speed (half or more of the speed of light) have more gravitational attraction to each other than they would if their relative speed were forty miles per hour. Thank you for your help. Jim Adrian
5. ### I Gravitational Mass of a Ball of Photons: Concept Q10.4 in Gen Relativity

This is based on "Concept Question 10.4" in Andrew Hamilton's General Relativity, Black Holes, and Cosmology. I have modified the question somewhat in order to focus on what seem to me to be the key issues. Suppose we have a spherically symmetric ball of stress-energy surrounded by vacuum. More...
6. ### I Any direct evidence of gravitational mass increase?

Is there any evidence that objects moving increasingly closer to light speed gain gravitational mass, in the sense of attracting surrounding (and not co-moving) masses more strongly, rather than solely possessing the increased inertial mass implied by the greater force necessary to...
7. ### B Relativistic Physics: Gravitational & Inertial Mass

In Newtonian mechanics, both gravitational mass and inertial mass is m. This principle is known as the principle of equivalence. However, I heard that in Relativity, gravitational mass is γm instead of m because total energy of the particle is γmc2. But in special relativity, it is widely known...
8. ### Inertial and Gravitational mass - Assertion Reason

Homework Statement [/B] Homework EquationsThe Attempt at a Solution I think the two masses , inertial and gravitational are equivalent and because of this fact , the ratio of the two masses is one . The correct option should be 1) . But the answer given is 3) i.e A statement is true and R...
9. ### B Gravitational Mass & Velocity: Is There a Correlation?

Hello! The equation for relativistic mass by special relativity tells us the relativistic mass for object in motion...but since inertia mass has same value as gravitational, does this formula also apply for gravitational mass? Thank you!
10. ### B Inertial and gravitational mass

Doesn't the postulation of the inertial and gravitational mass equivalence suggest that GR is not a complete theory? (since it also cannot be explained as a neccessity by the anthropic principle)
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### I How to prove gravitational mass & inertial mass equivalence?

There is a video on YouTube where Sean Carroll says for Newton it was just an accident that inertial mass equals gravitational mass, but with the general theory of relativity it became obvious that it has to be so. How does one see that? My own attempt has been consisting of transforming...
12. ### I Gravitational Mass of Photons: Passive & Active

As I understand a photon has zero rest mass (as far as we can tell) but it does have a passive gravitational mass in order for it to be able to respond to gravity. But I've been shown that passive gravitational mass should be equal to active gravitational mass, and if this is true and photons...
13. ### I Theoretical Possibility of "Opposite" Gravitational Mass?

This is an unusual idea that I have been entertaining for some time, and I can't find anything about it online. However, it is so simple that someone must have conceived it before. First, I will elaborate my idea, then I will ask if it possible within the framework of General Relativity. There...
14. ### Conceptual difference between gravitational and inertial mas

I know that this question has been asked many times before on this forum, but on every existing thread either the question or the answers, or both, were too vague. I understand that inertial mass is defined as the property of an object to resist change of its velocity, that is the mass that...
15. ### Gravitational mass defect

Hello, in nuclear physics we have a mass defect by the binding energy of the nuclides. A similar effect appears in the theory of gravitation induced by the gravitational binding energy, which reduces the mass. But for example at the ISCO of an Kerr black hole we have binding energys about...
16. ### Equivalence of inertial and gravitational mass

Is there any credible hard evidence that this equivalence extends to all moving bodies? We accept on good grounds that the apparent mass of moving objects is enhanced by motion, to a measurable degree that increases indefinitely as observed speeds of relative motion approach c. Likewise...
17. ### Relationship between inertial and gravitational mass?

I should preface this question by saying that I am not familiar with Einstein's general relativity, so I am trying to understand the relationship between gravitational and inertial mass from a purely classical standpoint. Newton writes that the gravitational force exerted by an object is...
18. ### Inertial vs Gravitational Mass

Hi! Could someone please explain the difference between gravitational and inertial mass? And how are they equal? Thank you!
19. ### Inertial vs Gravitational Mass "mystery"?

Hi everyone, I read in a first year textbook (K&K) that the reason why "gravitational mass is proportional to inertial mass" is a big "mystery"... Can someone please explain why this is a mystery? Thanks
20. ### Is it possible to decouple inertial and gravitational mass?

Or stated otherwise: Is it possible, due to other effects than mass for a non-spinning object with inertial mass n to exert a gravitational force characteristic of another non-spinning object with inertial mass different than n - theoretically or practically? I hope that covers all the caveats...
21. ### Ratio of inertial and gravitational mass?

what is the ratio of inertial mass to gravitational mass and how we can calculate it?
22. ### Estimating convergence of GRACE twin-satellites due to gravitational mass

Homework Statement Hello noble physicists, I am struggling to solve a problem with any sort of confidence whatsoever, so to you I turn in the hopes of guidance. The problem refers to GRACE twin satellite convergence due to gravitational anomalies. I’d like to estimate the...
23. ### Inertial Mass vs. Gravitational Mass

An interesting idea that my physics teacher posed to us yesterday, and apparently one that scientists have been puzzling over for quite a while: why is the mass as a measure of inertia equal to the mass in terms of gravity in our universe? My teacher said that this doesn't need to be the case...
24. ### Inertial and Gravitational Mass

Hi everyone! In an university examination it was asked to:"Explain the difference between inertial and gravitational mass" but my physics book is not very exhaustive on these differences. Which could it be a precise answer to this question ?
25. ### Difference between the inertial and gravitational mass

I'm trying to learn what is the difference between the inertial and gravitational mass. According to: http://www.physlink.com/education/askexperts/ae305.cfm and https://www.physicsforums.com/showthread.php?t=147282 there is practically no difference (as stated by the Equivalence principle)...
26. ### Gravitational mass defect, weyl metric

hello everyone, following the book of Landau&Lifsitz I managed to understand the Schwarzschild solution. At the end, it finds this formula for the mass of the spherical body generating the gravitational field: M=\frac{4\pi}{c^2} \int^a_0 \epsilon(r) r^2 dr in which \epsilon(r) is...
27. ### Does gravitational mass change during collapse?

When a body collapses under gravity, its initial gravitational potential energy is converted to kinetic energy and/or other forms of internal energy. At least that is how it is described in Newtonian gravity (not sure if this question is well-formed in GR, sorry). Now say that the collapse...
28. ### Do all observers agree on gravitational mass?

If I understand right, GR says that internal motions in an object add to its gravitational mass, because there is associated kinetic energy. My question is, do all observers agree on the quantity of gravitational mass? To an observer far away from the object, the object's internal motions...
29. ### Active and passive gravitational mass

Thought experiment: You are sitting on a platform which is sitting on a frictionless surface. I am sitting on a similar platform on the same frictionless surface next to you. If I reach out and pull you toward me, we will meet at our center of mass. If you reach out and pull me toward you, we...
30. ### Gravitational mass vs inertial mass

In Sean Carroll's lecture book is written: "... if gravitation did not couple to itself, a "gravitation atom" (two particles bounded by their mutual gravitational attraction) would have a different intertial mass (due to negative binding energy) than gravitational mass..." Would you please...
31. ### Inertial mass, gravitational mass, and the Higgs

If we explain the origin of inertial mass with the Higgs mechanism, how do we explain the origin of gravitational mass? In other words, how does the Higgs mechanism contribute to the gravitational field of a particle? (Note: the closest thread I've found to this is...

This is just a question out of curiosity. When things are traveling at a faster relative speed they are supposed to have greater mass which makes it harder and harder to increase their speed relative to the observer due to if being harder to overcome momentum. (Correct that if it has...
33. ### What doesn't have gravitational mass?

Is there anything in the universe that doesn't have gravitational mass? My understanding is that both rest mass and "relativistic mass" are gravitational masses, i.e. both are subject to the force of gravity. Further everything must have at least one or the other (if not both). Anything that...
34. ### Why is gravitational mass the same as inertial mass?

Gravitational mass is the property of objects that determines how they interact via gravity. For example how the Moon rotates around Earth. Inertial mass is an object's property that determines how much the object "resists" acceleration when force is applied to it. And it seems both are...
35. ### What are the standard units for inertial mass and gravitational mass?

[SOLVED] What are the standard units for inertial mass and gravitational mass? 1. What are the standard units for inertial mass and gravitational mass? And also apparently gravitational mass can be measured without gravity how can it be done? Thank you very much. My teacher said a hint is in...
36. ### Gravitational mass

On the basis that gravitational mass = inertial mass - does the gravitational mass of a particle increase along with its inertial mass when the particle is made to move? Bill
37. ### Gravitational Mass: Inertial vs Relativistic Mass

Does gravitational mass increase as inertial mass does in relativistic situations? Or does GR make this idea irrelevant?
38. ### Gravitational mass & inertial mass

Hey, first time here. I'm currently reading up on Physics, preparing for a selection test by myself. I need some help in understanding Newton's gravitational mass and inertial mass. Are they different? I read that there are some difference, and these masses ARE slightly different. Any reason...
39. ### Inertail versus gravitational mass

Hi, Inertial mass can be understood as the resistance to change motion. Gravitational mass exerts a pull on every other object (and as a result of action-reaction force law also on itself). It has been shown by experiment that both mass concepts are the same. But it looks strange that one...
40. ### Simple pendulum, and inertial and gravitational mass

Sir, A simple pendulum has a length L. The inertial and gravitational masses of the bob are m1 and m2 respectively. Then the time period of the simple pendulum is given by T = 2(pie)[m1L/m2g]^(1/2) {Read as 2 pie root m one L by m two g) My question is that the...
41. ### Active Gravitational Mass in GR

In the past I've spoken about mass a kagillion times. There was one aspect that I had to hold off on until I taught myself the details and meaning to a good level of understanding. I've now come to that level and have made another web page to describe it. The aspect I'm speaking of is "active...
42. ### Does Quickly Moving Object Have More Gravitational Mass?

In SR, when an object starts moving quickly, it seems to have more mass in the sense that it requires more force to accelerate it at a given rate. Dose the object also behave as if it has more mass in the sense that other objects are more attracted to it gravitationaly?
43. ### Graviton Theory: Inertial vs Gravitational Mass

gravitons ?? is the inertial mass proportinal to the gravitational mass in the graviton theory of gravitation ? I ask this because I can see easily how GR imply that the two masses must be equal since spacetime curvature acts at everypoint in the body. But with gravitons I can't understand how...
44. ### Inertial and gravitational mass

What's the difference between inertial mass and gravitational mass?