What is Mass: Definition and 1000 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. madafo3435

    Angular momentum: Grooved cone with a mass sliding down the groove

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  2. burian

    Trajectory of a mass element in a string overhanging a pulley

    Hello everyone, this is a thought experiment I made, it involves two ropes being pulled of a pulley similar to an atwood machine, and a block attached to the two pulleys at the other end. The ropes are being pulled at a constant velocity $ U$ from the end away from the block and the block rises...
  3. J

    I Changing the effective mass of an electron using electric potentials?

    The Dirac equation for an electron in the presence of an electromagnetic 4-potential ##A_\mu##, where ##\hbar=c=1##, is given by $$\gamma^\mu\big(i\partial_\mu-eA_\mu\big)\psi-m_e\psi=0.\tag{1}$$ I assume the Weyl basis so that $$\psi=\begin{pmatrix}\psi_L\\\psi_R\end{pmatrix}\hbox{ and...
  4. Helena Wells

    I Mass of the Moon and Gravitational Lensing

    During an eclipse the Moon covers the Sun.However this shouldn't be happening due to gravitational lensing we should be able to see some light? Is the mass of the Moon not big enough or photons do reach us but they are so little our eyes can't detect them?
  5. M

    Calculating Final Positions & Velocities for M1, M2 & Spring After DeltaT

    Let's say you have two masses on either side of a spring. Mass 1 is connected to the end of a spring. The spring itself has no mass. Mass 2 is free in space. So you have: [M1]-[spring] [M2]So it's more descriptive, I'll name the variables like you might in programming. Let's define...
  6. Nexus99

    Moment of inertia, center of mass and vincular reaction of a rod

    I'm struggling doing point 5, i have no idea how to solve that question. In point 1 i obtained the following result: ## I=\frac{ML^2}{2}## calculating the integral of dI, the infinitesimal moment of inertia of a small section of the rod of length dr. 2) Through the conservation of angular...
  7. Kiah Palmer

    Chemistry Mass of an element required for a chemical reaction equation

    Conversion: 9.65 kg = 9650 g Mass Al = 26.98 g/mol Molar Mass Al2O3 = (2 x 26.98) + ( 3 x 16.00) = 101.96 g/mol Mol Al2O3 = 9650 g / 101.96 g/mol = 94.65 mol Mol Al Required = 94.65 mol x 2 = 189.3 mol Mass 100% Al required = 189.3 mol x 26.98 g/mol = 5.107x103 g Mass 80% Al required =...
  8. Hamza M khan

    The center of mass of a semicircular arc of non-negligible width

    My attempt: 1) I am going to start this with a goal of setting up a reimann sum. First I divide the "arc"(?) of angle pi into n sub-arcs of equal angle Δθ 2) The total center of mass can be found if centers of mass of parts of the system are known. In each circular arc interval, I choose a...
  9. Kiah Palmer

    Chemistry Homework Help: Calculating Mass from Chemical Reaction Equations

    1a) Step 1: Balance the equation - S8 + O2 -> SO2 = S8 + 8O2 -> 8SO2 Conversion (t to g) 6.00 t = 6x10^6 g Molar mass SO2 = 23 + (2 x 16) = 64 g/mol 6x10^6 g / 64 g/mol = 9.375x10^4 mol SO2 reqired amount Sulphur = 9.375x10^4 mol / 8 mol = 1.172x10^4 mol S8 Molar mass S8 = (8 x 32)...
  10. Justinboln

    Calculate the New Velocity and the Velocity of a Pendulum Mass

    Question 1: A pendulum 2.2m long has a mass of 8.5kg suspended from it. The pendulum is initially in a vertical position and is moved to new position 35 degrees from the vertical. (a) How much work is required to move the pendulum to its new position? (b) If the pendulum swings from this...
  11. LCSphysicist

    Analyzing Net Forces and Equations in a Driven Mass on a Circular Path System

    What you think about this system:? F*cosw - k(x1+x2) - k(x1-x2) = mx1'' -k(x1+x2) - k(x1-x2) = mx2''
  12. udtsith12

    Mass loss in Bernoulli's Principle?

    Hi, I could really use help. I am trying to understand what would happen to the velocity of a freestream air if it loses mass while traveling down a tube. For example, suppose that you have 1 cubic meter of air traveling at 10 m/s down a duct with a 1m^2 cross section. And then suppose that you...
  13. LCSphysicist

    How to calc the period of this mass spring system?

    This is a problem very easy to deal with if we consider the effective spring constant, however, i want to avoid this solution, and see how to justify the period of this motion just by analyse the forces or the energy, what seems a little hard to me. First of all we would need to find the force...
  14. H

    I Mass Unit in General Relativity

    James Clerk Maxwell deduced that the unit of mass has the dimensions of (L^3)(T^-2). But he assumed Newton's Law. What would it be under general relativity?
  15. Nexus99

    A falling rotating rod strikes a ball of mass M....

    A homogeneous rod of length l and mass m is free to rotate in a vertical plane around a point A, the constraint is without friction. Initially the rod is stopped in the position of unstable equilibrium, therefore it begins to fall rotating around A and hits, after a rotation of ## \pi ## , a...
  16. T

    What is the relationship between force, acceleration, and mass in a lift?

    Much like the previous question I've posted I was quite unsure of the the method I should take and resorted after many attempts to just trial and error which resulted in getting the correct answer of 5kg after dividing the weight of 70N by 14ms^-2 (sum of upward acceleration and gravitational...
  17. sagigever

    Calculate the density of an object by the amount of displaced mass in water

    I have the solution for this problem but I did not understand the following statement: The mass of water the crown displaced is ##m = 740- 690= 50 g##. Therefore the volume of the crown is ## 50 cm^3## how can I conclude the volume of the crown from that displacement?
  18. andrewkirk

    1 pulley with mass, 1 mass on the cord, 1 external force, no gravity

    I remember, a few weeks ago, when looking for homework problems I could help with, seeing one as described in the title. I couldn't think of an easy solution and was busy at the time so i made a mental note to think about it later. I finally got around to doing that yesterday, and brushed up on...
  19. F

    I Understanding the mass of ordinary matter

    Hello, The periodic table contains 118 different elements which compose regular matter and the reality around us. On the other hand, "antimatter" is made of elements not included in the periodic table. As far as the periodic table, I think about 98 elements occur naturally while the other ones...
  20. Dale

    I What is the meaning of the mass assigned to an individual quark?

    A hydrogen atom is less massive than the sum of an unbound proton and an unbound electron. If I add energy to the atom the system becomes more massive, and when I add enough then I have an unbound electron and proton, each of which has the usual mass. So the mass of an electron is the unbound...
  21. draikens

    Chemistry Molar Mass Calc: My Solution | PDF File

    pdf file is my solooution l think its wrong
  22. kaycha

    Complex motion equation (projectile with changing mass and thrust)

    I need an equation to predict the flight path of a changing mass projectile under changing thrust. Any thoughts?
  23. L

    Chemistry Finding the mass of an aldehyde

    Aldehyde + H2 = alcohol Ethanal + H2 = ethanol This is all that I have done so far
  24. B

    Engineering Gyroscopic Precession - Mass of wheel & Angular Momentum

    Hello, I have this i am learning. I have been trying to find information online but have struggled to find anything which helps me. YouTube usually has good videos, but doesn't seem to on this. This is one topic i have never learned before. But keen to. I was hoping someone could help me...
  25. J

    Are There Any Alternative Brass Weight Sets for Lab Equipment?

    For the past 8 years I have used weight sets like the one below and they have been very versatile. But, just before Christmas, most of them were stolen. The person was nice enough to leave me some of the 100g and below masses. I've finally gotten permission to get new sets and now I can't find...
  26. Leo Liu

    Why do objects always rotate about their centre of mass?

    Why do unconstrained objects always rotate about the lines passing through their CMs when tangential forces are applied to them? I understand that if an object does not rotate about its CM, then its rotation will decay to the rotation about the axis passing through its CM. Also, when a roller...
  27. J

    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
  28. ttesss

    Newton's 2nd Law: Force, Mass and Acceleration

    I´m currently studying Newtons 2nd law and I don't get how can force only depend on mass and acceleration and not on velocity.. I mean, if I punch something with my fist going at constant velocity ( acceleration=0) it stills has a force right?
  29. George2020

    The relationship between friction and mass

    Mass is directly proportional to static and kinetic friction and inversely proportion to the coefficient of friction. Material affects the coefficient of friction as well as both static and kinetic friction. eg rough surface will have a higher coeffieiceint of friction
  30. Amirul96

    Mass and Volumetric Flow rate of Natural Gas

    Hi. I am currently doing my internship in the oil and gas industry (contractor) as process engineer. My supervisor give me a task to do some reverse engineering where i need to study how a spreadsheet (calculation) construct by other process engineer was been constructed. Ok the situation is the...
  31. J

    Chemistry Calculating the Mass of a Precipitate

    Hi there, I have a problem from an exam which I passed recently, however this was one problem I got wrong and I want to understand how to solve the thing. Now I shall detail the problem below. This is my subsequent attempt to solve it after the exam (so I don't know if this attempt is correct...
  32. S

    Center of mass energy for two relativistic colliding particles

    Starting from the center of mass energy S = (E_{1} + E_{2})^2 - (\vec{p_1}+\vec{p_2}) knowing that E^2 = m_{0}c^4 + p^2*c^2 one has S = (E_{1} + E_{2})^2 - (\vec{p_1}+\vec{p_2}) = ( m_{0}c^4 + p_{1}^2*c^2) + m_{0}c^4 + p_{2}^2*c^2)^2 - p_{1}^2 - p_{2}^2 - 2p_{1}p_{2}cos \{theta} and then...
  33. T

    What I do not understand about mass spectrometers

    I try to do my assignment which is based on mass spectrometer entirely. The mass spectrometer i am working on has these parts below: 1.Accelerator region 2.Velocity selector region 3.Spectrometer The elements i am working on are isotopes of the same element and they all enter the accelerator...
  34. astroYEEET

    Mass, luminosity and magnitude of a galaxy

    So i first calculated the angular area of the galaxy. a=22.6'' and a/b=0.85 => b = 26.588''( btw I do not know why a/b =0.85 since b is the semi minor axis). Then the area of the elipse is a*b*π =1887.745''. Then using the first equation we get an apparent magnitude of m=16.511. Using the second...
  35. G

    I Why does nothing happen at the Planck mass?

    It appears as clear to me that the Planck mass has a fundamental role, since for it the deBroglie wavelength and the Schwarzschild radius are equal. So it is some borderline between elementary particles and black holes. What intrigues me, however, is that the universe is mostly made up of...
  36. Islam Hassan

    I Mass & Radiation 3D Distribution in the Universe

    What percentage of the universe’s A) total mass —including dark matter— and B) radiation energy is estimated to reside in: Inter-galactic space covering i) inter-galactic medium and ii) distinct inter-galactic astronomical objects; and Galaxies covering iii) inter-stellar gas clouds, iv) stars...
  37. R

    B How the role of Mass is justified for below cases? (Earth/Moon, Jupiter/Io)

    How the role of Mass justified for the above cases in Newton's gravitation laws & in Einstein's GR?
  38. ElectronicTeaCup

    How can I calculate work done when raising a mass using W = 32r^2?

    I do not understand how to get ##W = 32r^2##
  39. J

    Static equilibrium: mass on beam

    A diagram of the physical situation is below: Choosing the positive ##y## direction to be upwards and the positive direction of rotation to be counterclockwise, Newton's linear second law gives: $$-m_D g + F_L + F_R = 0$$ where ##F_L## is the magnitude of the force exerted on the bar by the...
  40. R

    Mass spectrometer with a Lead element

    Summary:: How to load the plates with the Lead element in the spectrometer I have a mass spectrometer with lead element which has an electronic configuration 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 4d^10 5s^2 5p^6 4f^14 5d^10 6s^2 6p^2. It has 2 free electron, so the ejected electrons go...
  41. S

    Do photons, phonons and electrons have mass?

    These articles have energy but do they have mass?
  42. Arman777

    A N-body simulation with varying neutrino mass

    I am trying to find a picture of the N-body simulations that shows the LSS. Particularly I am looking for different neutrino masses without the CDM. For instance pictures likes this But with more varying/different neutrino masses. I am looking for articles
  43. person_random_normal

    I Visualizing the Fourier transform using the center of mass concept

    I found this video on youtube which is trying to explain Fourier transform using the center of mass concept At 15:20 the expression of the x coordinate is given in the video. I believe it is wrong, and it should be: ##\frac{{\int g(t)e^{(-2 \pi ift)}.g(t).2 \pi f.dt}} { \int g(t).2 \pi...
  44. Y

    Moment of inertia where mass and torque are at a different positions

    The formula for moment of inertia is: I=mr^2 A common derivation for this is: 1. F=ma 2. τ=rma 3. τ=rmrα = r^2 mα This is a rotational version of Newton’s second law, where torque replaces force, moment of inertia replaces mass, and angular acceleration replaces tangential acceleration...
  45. K

    Cantilever beam deflection with point mass and point load at the end

    Hi all, I was looking for help with obtaining deflection at end of a cantilever beam with point load at end as well as point mass at the same location. I believe it would be exactly same. Is this correct? That is, I think just adding point mass at the cantilever's end wouldn't change the...
  46. LCSphysicist

    Find the period of a pendulum consisting of a disk of mass M

    I did the first step pretty well, and the answers match, but i don't understand why in the second case the period changes.
  47. J

    Chemistry Find the mass of one element of a sample

    1 mole of K2CrO4 has formula mass of ((2 x K) + (1 x Cr) + (4 x O)) g => ((2 x 39.0983) + (1 x 51.9961) + (4 x 15.9994)) g = 194.1903 g we have 2 moles of K in 1 mole of K2CrO4 = (2x 39.0983) g = 78.1966 g so for 1 mole of substance we have 78.1966 g So how many moles of the substance do we...
  48. jamiebean

    A mass being pushed up an inclined plane

    i tried to solve the problem with the above way then i calculated Fg= mass x 9.8 = 242.06 N FgII= Fg x sin50 =185.4287N so the force required is 185. is this correct?
  49. S

    New amplitude of a spring-mass system when a 2nd mass falls on the first

    I am confused about conservation of momentum for this question. I take the system as two objects, each having mass m. For first object (the one performing simple harmonic motion), there is net external force acting on it in horizontal direction (restoring force of spring). For second object...
  50. Den tredje

    A mass collides with a stick and they stick together....

    (Note: the stick weight is 0.4kg not 1.0kg) Im not a native English speaker. So please excuse my bad english. I had this on my exam, and Ím really unsure what the answer to this is. Ím suppose to calculate the hight and angle of the swing Of this stick after a “stuck together” collition. But...
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