Mass Definition and 1000 Threads

Why for gravity some things like planets, stars are heavy enough to have a gravity so they don't fall of the space? When a small object can free fall in space, why a planet has a gravity, and they are considered heavy to what formula?

Could you please help me with this? I guess move of the mass will be determined with kinetic friction.

Hello , I read the earth and the sun has a mass and google etc gives a measure . When I go the supermarket and buy 1 kg of bananas , they are weighed on scales . Is science lying about the mass of the earth and the sun ?

I hope i made clear what i mean and i really hope i can get my answers here Thank you very much for answering already

I see this system as essentially a simple pendulum. The mass of the wheel seems irrelevant, because it is distributed uniformly in such a way that it cannot affect the oscillation. The first formula above for rotational inertia is the only one I know for a simple pendulum that includes mass...

The answer should be around 39g. I keep getting around 45g. This is the calculation I tried Any feedback on what I am doing wrong ? Regards!

i just watched this: and now im wondering, jsut as when the atom bomb converts mass into energy and we can measure it in force and heat and electromagnetic radiation of various wavelengths, obviously just grams, but of what? what particle would we say is representing the 99% of a proton's...

Newtonian gravity is the force law such that for any mass M, the circular orbit of any test particle m at a distance equal to the Compton length of M has the same areal speed, independent of M and m. I wonder, have you seen this sort of definition online in the literature? I guess that...

I can't figure out how to prove this using only those two identities? I mean in general, I could prove it easy when using relativistic equations, and showing that if ## v = c##, the denominator becomes 0, and if ## v>c##, the denominator becomes an imaginary number (a negative square root)...

Given that physics is the study of the physical world, what exactly is spacetime if it is an actual "real world thing", a curved medium or "fabric" guiding the movements of masses, and what is the physics of how this guidance works. As far as I know, space is a vacuum (where not occupied of...

This pop up on anyone radar? Electron mass different throughout the universe? I don't see how this section could have passed peer review: The masses of electrons, muons, and tau can be explained by the different curvatures of universe, galaxy, and solar system, respectively. I've seen crazy...

According to the dark matter theories is the total percentage of the dark matter's mass across the Universe remains constant as time passes?

I know that I can draw an FBD and apply Newton's 2nd law to find the relevant equations. But my question here is why is the mg vector or the weight of the entire rope same at every point on it I mean to say that if the mass of the entire rope is say M then how can a small point on the rope also...

Does the time to the collapse of a particle system depend mainly on its mass/momentum, or complexity? For example macroscopic object. If system is quite isolated, is no spontaneous collapse even massive or complex systems?

First, I did read this article on Byrons: https://www.physicsforums.com/insights/a-beginners-guide-to-baryons/. If the answer to my question is in there, I'm sorry, but I missed it somehow. Honestly, much of that article went over my head. Other than that, it's as the TLDR says. I have heard...

In p. 84, Zee says “In the new coordinates, M is replaced by M’ = R[-1]MR.” However, I figure out M is replaced by M’ = RMR[-1]. Why is M replaced by M’ = R[-1]MR?

Mass of honorite initially: 4.51 kg at 261.2 K Additional mass of honorite added: 3.75 kg at 261.2 K total mass of honorite is 4.51 kg + 3.75 kg = 8.26 kg Mass of liquid odium: 14.69 kg at 391.14 K Q melt = m honorite × L honorite Qmelt = 8.26kg × 15500J/kg Qmelt = 128030 J Q cool = (m odium)...

I don't really get why applying different forces to objects of different masses would result in different accelerations. I read my textbook, and I understand the formula F(net) = m*a, and I think the reason may be because mass is inversely proportional to acceleration ? But this doesn't really...

Dear community, I have a question comparable to https://www.physicsforums.com/threads/calculating-the-mass-of-air-in-a-pressurised-air-tank.1053707/, but with some additional peculiarities. My setup is: 1) I got a time series of gas pressure and temperature, with a time step of 2 minutes 2) I...

I can calculate the COG with the above formula however P2 is unknown. I need to be able to put P2 into another function which will check that the vector A->COG is parallel to the nominated angle. I cannot seem to work this one out algebraically. Any assistance or guidance would be appreciated.

Assuming I have a given wavelength λ of the hydrogen spectrum and I want to calculate the nuclear mass of the isotope, is my approach correct? Rydberg-formula: $$\frac{1}{\lambda} = R_M \left( \frac{1}{n_1^2} - \frac{1}{n_2^2} \right)$$ with $$R_M = \frac{R_\infty}{1 + \frac{m_e}{M}}$$...

Let ##m_{r}=1## kg be the mass of the rod and ##m_{s}=0.5## kg be the mass of the sphere. ## \tau = -rFsin\theta ## ## = -r([m_{r}+m_{s}]g)sin\theta ## ## =-1.3(1.5)(9.8)sin30 ## ## \tau = -9.6 ## My book's answer key disagrees and my initial thoughts are that maybe the mass in my...

I suppose to keep the pulley from rotating the net torque has to be zero? Let ## F_{r} ## be the force that the 5 kg mass on the ramp exerts on the pulley and ## F_{d} ## be the force exerted straight down by the other mass on the pulley. Let ## r = 0.3 ## m be the outer radius of the pulley...

Imagine making a hole in the ground, about a mile deep, with a large and square diameter. In the middle of the hole, there is a hollow and narrow tube with all air sucked out. Next to one of the walls, so close that it's touching, there is another hollow tube without air inside. Two identical...

I was recently very surprised when I had a looked up relativistic kinetic energy. All sources gave the kinetic energy as the difference between total energy and rest energy, in some or other variant of the formula ##E_k=(\gamma−1)mc^2##. I didn't really understand at first. It seemed overly...

Until very recently I thought that according to general relativity masses curve spacetime as a whole, i.e. the complete abstract 4-dimensional spacetime. It came as a complete surprise to me to learn that you can take away the time-component and are left with a curved 3-dimensional space, which...

In the 2nd question, I definitely think it's D, because the force the rock exerts on your toe is equal in magnitude to the normal force the toe exerts on the rock which in turn is equal to the rock's weight, which is related to m by the constant g. In the 1st question, I am not as certain, but I...

I have read widely about spacetime but not deeply. I am not good with high mathematics. I am aware of and comfortable with the concept: “matter tells spacetime how to curve, and curved spacetime tells matter how to move.” But not much deeper. This is a thought experiment. Is there an equation...

So I've been searching around for rigorous explanations for things like ##dx## in physics, I'm not looking to fully commit myself to reading the relevant literature at the moment but just want to know what I'll have to do in order to understand. Perhaps I'll make a separate thread about that...

So, the first thing that came to mind when I was trying to figure out how to set this up is that it will be a dU problem. After trying to figure out how to set it up to no avail, I took a look at how they solved it in the solutions manual. It's making absolutely no sense to me... They state...

TL;DR Summary: I have the aforementioned m/z and a mass spec graph, my lecturer completely glossed over how to find the molecular formula so I'm stumped. I have a mass spec with 4 peaks and the m/z value, how can I find the molecular formula.

Suppose there was a 4th generation of neutrino (X, say) with mass m ~ 1 keV. The other three neutrino generations decouple at T ~ 1 MeV and are not heated during ##e^{\pm}## annihilation (whereas the plasma is heated, leading to a bookwork ##T_{\nu}/T_{\gamma}## factor due to conservation of...

I have tried to answer this using the relevant equations I am provided on my formula sheet, however I get stuck pretty close to the end. I start with 1/2mv^2=1/2kx^2 at the equilibrium position, and kx=mg, x=mg/k. This gets me to v^2=mg^2/k, but I don't know where to go from there. The potential...

If one were to demonstrate gravity independent of earth's constant gravity, how could it be done? Assuming this would need to be done in space, what minimum proportions of mass would be required to demonstrate gravitational pull to a human's naked eye?

should I be expecting a higher amplitude at resonance for a mass that's heavier to an extent form another where each is attached to a spring vertically , I assumed that's true since the heavier mass will stretch the spring more meaning when moving like a sin or cos wave the amplitude...

What are the independent and accurate ways of determining stellar mass apart from its gravitational effect?

According to STR: E=MC^2. When an electron and proton are independent( without influence of any kind of fields, especially electrostatic fields )their rest masses are Me and Mp. When they combine to form Hydrogen atoms they emit photons. So, some energy loss in the form of photons. So, now...

I can't possibly be the first to notice this numerical coincidence, but my search skills are inadequate to find information about it, and I was hoping others could point me toward papers on the subject. Neutron mass, mN: 939565420.52 (54) Proton mass, mP: 938272088.16 (29)...

How can i calculate the Energy required to bring 1 kg 1000 meter above the surface of the earth ?

Dirac ("GTR" p. 47) makes an interesting observation immediately after obtaining Einstein's field equations with the simple energy-momentum tensor ##T^{\mu\nu}=\rho v^\mu v^\nu##. (##v^\mu## is the four-velocity.) First, the conservation of matter ##\left( \rho v^\mu \sqrt{-g}...

Teacher says Im wrong on both these questions. I have consulted with other teachers and they say im correct. What do you guys think? 3. As mass increases, so does terminal velocity. 5. Fnet = FDrag - Fg ma = FDrag - mg FDrag = 79(8) + 79(10) FDrag = 632 + 790 = 1422 N Teacher Comments 5...

According to Einstein's formula, energy is generated when mass is obtained or lost. What does losing or gaining mass mean for an atom or particle valence? It's simply because of the formula I don't want this kind of answer I want. What does it mean for an atom or particle to lose or gain mass...

It is said that the universe is made up of approximately 4.9% ordinary matter, 26.8% dark matter and 69.3% dark energy. Why isn't ordinary energy included in this "pie"? I suppose it is included within ordinary matter, but could it be calculated what % are particles with mass and what % is pure...

Black holes accrete mass around them and it falls gradually up to the even horizon where mass is trapped by the black hole forever. However, the rate of mass falling from the accretion disk to the black hole ranges from being very fast to very long-lived, depending on various conditions...

Stuck on (c), part (i). Any ideas about what is the most elegant way to prove it, maybe using Mandelstam variables since this exercise is supposed to be about them?

The Hamiltonian for a scalar field contains the term $$\int d^3x m^2 \phi(x) \phi(x)$$, does it changs to the following form? $$\int d^3x' {m'}^2 \phi'(x') \phi'(x')=\int d^3x' \gamma^2{m}^2 \phi(x) \phi(x)$$? As it is well known for a scalar field: $$\phi'(x')=\phi(x)$$ .

Is there a typo in this question? Supposing there was no friction, the block would fall until the force of the spring was equal to ##mg = 2 * 9.8 = 19.6##, taking the upward y direction as positive. Since ##F_{spring} = -200y## and ##19.6 = -200(-0.098)##, the block would fall 9.8 cm. It's not...

Hi guys i have this exercise: A particle of mass m, confined in the segment -a/2 < x < a/2 by a one-dimensional infinite potential well, is in a state represented by the wave function: 1. Determine the constant N from the normalization condition. To do this, I have to integral the square...

I think that both kids experience the same acceleration (irrespective of mass) since the only force pushing them downwards is acceleration due to gravity, which is the same for both of them. Thus, since they start sliding down the hill at the same time (assumption), and are accelerating at the...

This is meant for our younger readers who have only seen popular accounts of where mass comes from. They often say it comes from the Higgs boson, which is sort of true. But it is deeper than that. Sabine has given a deeper popular account in the following video: As an aside, forget this...