Mass Definition and 1000 Threads

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

    Calculating Hydrogen Mass Storage in Compressed Vessels

    Hello all; I am looking for an equation for calculating mass storage of Hydrogen in compressed vessels I have fount the following link (https://nanosun.co.uk/hydrogen-tools) which provides what i need but would like to create something similar for internal use Can you suggest an approach to...
  2. DuckAmuck

    I Invariant Mass in Gravitational Fields: Special Relativity

    In Special Relativity, you learn that invariant mass is computed by taking the difference between energy squared and momentum squared. (For simplicity, I'm saying c = 1). m^2 = E^2 - \vec{p}^2 This can also be written with the Minkowski metric as: m^2 = \eta_{\mu\nu} p^\mu p^\nu More...
  3. lilymay992

    What is the maximum speed of a proton if its kinetic energy is 1.28x10^-14 J?

    So first I tried to use KE=1/2 x m x v^2 but then realized I didn’t have the velocity and I can’t figure out a way to obtain it. I then tried to work out the energy using a different equation, W= q x v but that left me with 1.28x10^-14 J which seemed too small. I also then have to calculate the...
  4. L

    I Does Curving Space by an Approaching Mass Do Work?

    A thought experiment. Two rigid, concentric rings, joined together by a series of lightweight elastic radial spokes. These rings and a heavy mass are approaching each other, such that in the frame of the rings, the mass is traveling along the central, perpendicular axis and will pass through the...
  5. J

    B How physics equations transform under inverse of parameters

    It is obvious that there is a one-to-one relationship between real numbers (defined to include infinity) and their multiplicative inverses (assuming we map the inverse of zero to infinity and vice versa). Thus, one should be able to replace the distance between two points in space with it's...
  6. F

    Can't find the effective mass of a 2-dimensional semiconductor

    This is the situation: you have the band structure of a two-dimensional semiconductor E=E(k). Both, valence band and condcution band. You use the definition of effective mass: (m)^(-1)=(d2E/dkidkj), but both bands are in such a way that the 2x2 matrix that you obtain has zero determinant. So...
  7. N

    Force exerted on a rope by a falling mass

    Hi I'm wondering, if I had a mass of 10kg and I dropped it 10 metres, how would I work out how much force is exerted on a rope? The rope is made of rubber bands
  8. Lone Wolf

    Finding the center of mass of a homogeneous object

    The object is: My attempt at a solution: I divided the object into 3 different rectangles and found the coordinates for the center of mass of each one, considering the origin at point "O". Then I found the mass of each rectangle, assuming the object has an area density of σ. m1 = 15σ; m2= 6σ...
  9. C

    Could somebody please explain the vapor compression cycle?

    Heat is taken from food in the refrigerated space to the evaporator which has evaporated (I am assuming saturated vapor) refrigerant flowing through it. My first stumble would be, if this is true, why doesn't the temperature increase for the fluid coming out of the evaporator (unless it is...
  10. D

    I What is the Most Accurate Mass for Rigel?

    I see so many different sources using different masses for Rigel. The most common of the bunch seem to be 17-18 solar masses. There are also a couple that give it 24 Sol masses. One astronomy book even cited it as 23, and another at 20. I cannot stand this discrepancy and would like to know what...
  11. badger1999

    Rotating Disk and Hanging Mass Calcululations

    I used the above equations to solve for tension, torque, inertia, and angular acceleration. Are the formulas I used correct for the given system? How can I calculate Inertia from the trendline equation, I'm drawing a blank.
  12. T

    Bouyancy force -- What mass can the balloon carry?

    In a I used FBouyancy - FBalloon -F mass = 0 rewrote mass as a product of density and volume to obtain; m= v(densityair - densityHe) m= 1031.5kg.I am stuck in part b. I have this formula called Barometric formula which ı should use; P = P0 * e((-P0*g*h)/ P0 So what I understood is that...
  13. M

    Mass in motivic quantum gravity

    From the proceedings of Group32, the 32nd International Colloquium on Group Theoretical Methods in Physics (9–13 July 2018, Prague): https://iopscience.iop.org/article/10.1088/1742-6596/1194/1/012097 M D Sheppeard Abstract: A physical approach to a category of motives must account for the...
  14. koiuuuuuuuuuuu

    Weight vs. Mass: Explaining the Difference

    In class we do Science and I have faced with the problem between Weight and mass. Tutor told us that the weight is the force that causes everything to move. Mass is the kg .Why then, people ask other people what weight are you? Explain please. Thanks
  15. W

    A The problem of the mass of a body

    if we have known the density functionρ(r),and then we can calculate the total mass of a spherical body. M=integral of ρ. Now we will say that body has mass M, but I think it is wrong. according to special relativity, mass is equal to energy, so we can also say that body has total energy M,but i...
  16. parazit

    Mass of the fuel consumed at the reactor each year?

    Hi fellows. I am dealing with the following question and any help to solve it will be a huge favor. Let us consider a nuclear power plant which delivers 100 MWe. The plant is based on a Rankine cycle, where the steam exiting the reactor is at 350 C and water exits the condenser at 20 C. The...
  17. K

    I What happens to the inertia of a mass falling into a black hole?

    What happens to the inertia of a mass falling into a black hole? I am not even sure if I frame the questions correctly. Will this mass reach the center or is mass distributed within the black hole? Is the singularity the whole volume of the black hole or is it a point in the center? If a large...
  18. Eucliwood

    Work done on an object given a variable mass

    I was just doing some review on my physics lecture and I stumble on the idea of what if there was an object hanging and the cord mass is also included in the weight and it's displaced upward without having velocity nor time hypothetically and the cord change mass. I tried solving it by W = fΔx...
  19. koulbichok

    A Abundance and mass spectrum of PBH

    Hello. I'm trying to study primordial black holes for my work, but I still can't understand what are abundance and mass spectrum? Could you explain? Thanks in advance.
  20. A

    I Understanding the Relationship Between Mass and Matter

    No I'm not dumb, just confused. I keep reading that mass is the amount of matter. So is a 1kg mass matter? Is mass the stuff made of things . So when we say 1kg are we talking about the material? Or is mass the measure of how much? Looking for basic help. I always think about mass as how much...
  21. Nic sign

    Where Is the Opposite Force on a Pipe with Mass Flow?

    Lets say if I have a pipe with one end closed, and drill a small hole on the side of the pipe near the closed end. Then I use vacuum at the open end to create mass flow exiting the pipe. Where is the opposite force on the pipe? [crackpot youtube video deleted by moderator @russ_watters ]
  22. A

    A statics problem with a mass on the end of a string

    I have this problem. I know G, alpha and mu. I need to know theta for equilibrium. My problem is that in place of the thread I need to have a tension and when i write the equations of forces on all 3 axes and then I apply the conditions that Ff<=mu*N (Ff-friction force, N-normal on plane...
  23. A

    B Factors contributing to the atomic mass of an atom

    I was studying about atomic masses and realized that even if we say that the atomic mass unit corresponds to 1/12 of the mass of a carbon atom. why is it that even particular isotopes of elements have atomic mass in decimal values. 1/12 of a carbon atoms mass should equal to the mass of a...
  24. Y

    Problem concerning a mass with charge in a homogeneous electric field

    I know how the answer is C, since E=F/q and F=ma=mg. However, I am a bit confused as to why my other method doesn't work. I thought that since the droplets are falling at a constant velocity, there is not net force, so according to E=F/q the electric field must be zero then? This seems like a...
  25. WhiteWolf98

    Fluid Dynamics - Mass Conservation, State Equation for an Ideal Gas

    I understand that ##\dot m=\rho Q## and ##{\dot m}_{in}= {\dot m}_{out}## . So one can say that ##\rho Q_1 = \rho Q_2##. But I'm not sure if that equation is correct. I don't know if the density remains constant, or the volume flow rate. And then how I'm also supposed to tie a state equation in...
  26. W

    A Does Komar Mass Include the Energy of Gravitational Field?

    Does Komar mass include the energy of gravitational filed or just only the energy of matter. For instants, we calculate the Korma mass of Schwarzschild space-time and we get the result that is M, which is the mass of central star. Does that mean Komar mass only contain the energy of matter not...
  27. C

    For a throttling valve, why is it that temperature remains the same?

    For a throttling valve C.V analysis, I am wondering why is it known that temperature remains the same for ideal gases. I understand that using the energy balance equation, I end up with h1=h2. Pretty simple so far. By breaking down enthalpy into its components u1+P1v1 = u2+P2v2 I realized that...
  28. B

    AQA physics paper On potential energy in mass spring system

    The spring constant of a helical spring is 28 N mñ1. A 0.40 kg mass is suspended from the spring and set into simple harmonic motion of amplitude 60 mm. i use the equation 1/2 change in extension times by force where the force i assume is mass times by 9.8 but the mark scheme uses 1/2 kx ^2 and...
  29. K

    A Any developments on the origin of mass by QCD?

    Below I refer to the following article: The Weight of the World Is Quantum Chromodynamics Andreas S. Kronfeld Science 21 November 2008 Vol.: 322, Issue 5905 - pp. 1198-1199 I've been trying to find more information on the subject but it's been hard for a Google peasant like myself. Just the...
  30. TerranIV

    I Particles w/ 0 Inertial Mass Traveling Faster than Light?

    I was just curious if there were any known (theoretical) particles with zero inertial mass that don't travel at light speed. Is this even possible?
  31. PCal

    Calculate the actual fuel:air ratio by volume and by mass

    By Volume: Butane 0.75x6.5= 4.875 moles of O2 Propane 0.1x5= 0.5 moles of O2 Butene 0.15x6= 0.9 moles of O2 Total O2 4.875+0.5+9= 6.275 moles Air required 6.275/0.21=29.88 moles/m^3 With 10% excess air 29.88x1.1= 32.868moles 1 mole fuel:32.87 moles of air By Mass: CO2 Moles...
  32. J

    I How can a photon have no mass if it has momentum?

    My personal course of study in quantum mechanics hasn't brought me this far and so this question may be incredibly naive, but it has still been troubling me. If the energy of a photon is E = (hbar)(omega) and the units of hbar are J*s (obviously), then how can a photon have no mass if a J is...
  33. Alif Yasa

    Finding the speed of the cylinder's point of mass

    I already got the answer for the case a but at the case b, i don't know how to sum all of the torques. I'm thinking of using integral, but i don't know where to put the pivot point for the torque. I don't know how to search for the pivot point. Can anybody give me hints so i could find the pivot...
  34. P

    Intuition behind centre of mass equation for a rigid body

    So my basic understanding of an integral is that it finds the area underneath a graph. I understand the idea behind an integral being the summation of f(x) * delta x, where delta x approaches zero. If I look at the integral it's telling me that there's a change in mass that is being...
  35. G

    I Antimatter atoms vs atoms with greater mass?

    I was just kinda wondering about this the other day and can't seem to find an answer on Google. Basically I'm wondering what would happen if an atom of anti-hydrogen for example, came in contact with a normal matter atom of greater mass, say a gold atom. I'm figuring that the positron and...
  36. Daniel Wareham

    B Is mass the only store of energy

    After thinking about E=MC^2, I thought that mass is the only store of energy. I have found many “stores of energy” that are actually just increase in mass. For example kinetic energy, it’s not a store of energy by itself, it’s actually because of special relativity that it has more mass. When...
  37. Leonardo Machado

    I Myers mass formula to find the valley of stability for A=56

    Hi everyone. I'm currently trying to master the use of the formula for nuclear masses from MYERS AND SWIATECKI (1969), https://www.sciencedirect.com/science/article/pii/0003491669902024. $$ E=[-a_1+J\delta^2+0.5(K\epsilon^2-2L\epsilon \delta^2 +M\delta^4)]A+c_2 Z^2 A^{1/3}...
  38. C

    Mass of Hadrons: Verifying Special Relativity

    Hmm the mass of a hadron is an example of the verification of special relativity.The total mass of the quarks isn't equal to the mass of a hadron at rest frame.But quarks are moving very fast due to strong interaction and they gain mass (mass-energy equivalence)
  39. A

    B Does an orbiting mass exert force on what it is orbiting around?

    I'm trying to get this concept straight in my head. Take, for example, the International Space Station; it is orbiting the Earth in considerable gravity, yet the inhabitants feel weightless. So they cannot be exerting a force on the Earth aside from their own minuscule gravitational pull right...
  40. C

    What is the intuitive meaning behind the polytropic process.

    What does it actually mean from an intuitive standpoint? I don’t want to simply memorize the equation. What is it really and when can it be used? What is the usefulness of it? Thanks.
  41. C

    What is the difference between flow energy and boundary work?

    What is the difference between the two? Also, as another question, for enthalpy, is it correct to define it to be the sum of internal energy and flow energy or is there another understanding for it? Thanks in advance
  42. C

    Why is air in atmospheric pressure and room temperature a gas?

    This seems like a simple thermodynamics question but I would like clarification. So the absolute critical temperature is 132.5 K (-221.17 F) and the absolute critical pressure is 3.77Mpa (546.7 psi). I understand that for temperatures above the critical point, a pure substance undergoes an...
  43. C

    How does specific volume play its role in the phase diagram?

    So, I am casually sifting through a chapter in a thermodynamics textbook talking about the multiphase process that pure substances go through. I understand how the P-v and T-v diagram works and that out of the three properties (specific volume, temperature and pressure), two of them are...
  44. Shivang kohlii

    Shm , calculation of amplitude of spring mass system

    Homework Statement In A spring mass system , the spring stretches 2 cm from its 's frelength when a force of 10 N is applied . This spring is stretched 10 cm from it's free length , when a body of mass m = 2 kg is attached to it and released from rest at time t = 0 . Find the A) force constant...
  45. P

    I Center of Mass of a jetpack-Earth System

    It is known that the center of mass of an isolated system will assume the same location no matter what internal forces there are (as long as no net external force occurs). My first question is if there exist two bodies of masses m1 and m2 in some space that has no friction, gravity, or...
  46. aleah

    Calculate elevator acceleration using mass

    Homework Statement A man with a mass of 65kg is traveling in an elevator and stands on a set of scales, at a given instant the scales measure his weight to be 72kg, find the acceleration of the equation Homework Equations f=ma w=mg FN =mg+ma[/B] The Attempt at a Solution [/B] I know that...
  47. K

    Automotive Dual mass flywheel clutch - How does it make a difference?

    I was going through these two documents: https://www.schaeffler.com/remotemedien/media/_shared_media/08_media_library/01_publications/schaeffler_2/symposia_1/downloads_11/4_DMFW_1.pdf http://www.partinfo.co.uk/docs/140 My primary interest was to understand why and how Dual Mass Flywheel (DMF)...
  48. A. Neumaier

    I Redefining the Mass Unit: Counting Particles for Precision

    Can you give details?
  49. K

    4 momentum mass non-conservation, special relativity

    Homework Statement A particle with mass M and speed v along the positive x-axis hits a stationary mass m. Two particles, each with mass µ, emerge from the collision, at angles with respect to the x-axis. (a) Write the equation for conservation of the 4-momenta, for arbitrary angles θ_1, θ_2 of...
  50. M

    Torque required to tilt 1200 kg mass?

    Object to be tilted = 1200mm diameter cylinder Cylinder height = 2.5 meter weight of tilting assembly = 1200 kg Cylinder is on platform which is "L" shaped and tilting point is on that corner of "L" as in attached image. Shaft diameter on which it is tilted id 63mm Angular acceleration = 0.05236...
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