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. J

    MHB Can you calculate the total mass of three parcels at a post office?

    At a post office, there are three parcels of different masses. The mass of the first parcel is y grams. The mass of the second parcel is 500 grams greater than that of the first parcel. The third parcel is 210 grams lighter than the first parcel. a) Find the total mass, in grams, of the three...
  2. I

    Chemistry How to get moles from MO having % of mass?

    Homework Statement This is a question from a chemistry book Two oxides of a metal contain 27.6% and 30% of oxygen respectively. If the formula of the first oxide is MO, find that of the second? 3. The Attempt at a Solution In the first MO, if the total amount is 100g, then O is 27.6g...
  3. M

    Continuity equation and mass flowing through two pipes

    Can we apply continuity equation between the given two cases? The only difference in the second case is that the pipe of diameter d2 is replaced by a pipe of diameter d3. Will the mass flow rate be same for both the cases.
  4. S

    Finding the acceleration of the center of mass

    Homework Statement Two forces F1 →= 2i ^ + 3j^N acting on a mass m1 =1.5 kg, andF2→= i^+ j^N acting on a mass m2= 1.0 kg.The magnitude of the acceleration of the center of mass of the system is?
  5. L

    I A question about invariant mass

    A question of invariable mass. In a inertial system, the invariable mass of a system never change with time. This system may not be an isolated system. Whether in any inertial system, the invariant mass of the system remains unchanged.Or, in a certain inertial system, what is the necessary and...
  6. MARX

    Kleppner:Mechanisc: 7.33 Grooved cone and mass

    Homework Statement A cone of height h and base radius R is free to rotate around a fixed vertical axis. It has a thin groove cut in its surface. The cone is set rotating freely with angular speed ω0, and a small block of massm is released in the top of the frictionless groove and allowed to...
  7. M

    Problem about a rigid body pulled by a mass

    Homework Statement A solid body consisting in two concentric disks of masses m1, m2 and radius r1<r2 is linked through a ideal rope to a mass m which falls down with a certain acceleration. The solid body moves of pure rolling. Find the acceleration a of the mass. Homework Equations P-T=m*a...
  8. HCverma

    How to get atoms of something having % of mass?

    Homework Statement Two oxides of a metal contain 27.6% and 30% of oxygen respectively. If the formula of the first oxide is MO, find that of the second? Now my problem is how to find the atoms of O from the masses of 27.6% and 30.0 %? Homework EquationsThe Attempt at a Solution I can see that...
  9. caitphys

    Circular orbit change after gaining mass ejected from sun

    Homework Statement A satellite of mass m is in a circular orbit of radius R about a star of mass M. The star ejects 1% of its mass by means of a spherically symmetric wind which removes the mass to a large distance. What are the new nearest and furthest distances of the satellite’s orbit around...
  10. HCverma

    12 amu and 1.9924 X 10^-23g express the mass of a atom of C?

    Homework Statement 12 amu and 1.9924 X 10^-23g express the mass of an atom of C? Homework EquationsThe Attempt at a Solution Do 12 amu and 1.9924 X 10^-23g express the mass of an atom of C? As I know, 6.023 X 10^23 atoms of C weighs 12 g, 1 atom of C weighs 1 X 12 / 6.023 X 10^23 = 12 amu...
  11. HCverma

    What does it mean by 1 amu? The mass of a proton?

    What does it mean by 1 amu? the mass of a proton or a neutron or an electron? If the mass of O is 16 amu, then what makes 16 amu in O atom? 16 protons or 16 neutrons or 16 electrons?
  12. F

    Experiments about impact of mass in different areas

    There's important experiments showing the equivalence of inertial mass and gravitational mass ( the Eotvos experiments), but I couldn't really find many that show the equivalence of mass (or the stress-energy tensor) in other contexts. These are some of the variants of mass I'm interested in...
  13. G

    A Charged particles mass before symmetry breaking

    How could electrically charged particles be massless before the symmetry breaking? Wouldn't the energy stored in the electric field contribute to particles mass?
  14. T

    B Why don't high mass stars expand and cool?

    When a high mass star starts to fuse heavier elements, the core heats up the outer layers enough to for them to begin fusion of their own. My question is: because the star hasn't gained any mass, but it has increased in temperature a lot, why doesn't the star expand and cool like a red giant...
  15. HCverma

    Is AMU the unit for both 'atomic mass' and 'molecular mass'?

    Is 'AMU' the unit for both 'atomic mass' and 'molecular mass'?
  16. HCverma

    Does 'molar mass' include an atomic weight for single atom?

    Does molar mass include an atomic weight for single atom and molecular weight for molecules?
  17. S

    Rod w/ Pivot and Attached Mass Pendulum

    Homework Statement A solid rod of length L and mass M has a pivot through its center and is originally horizontal. Another mass 2M is then attached firmly to one end of the rod, and released. What is the maximum speed of the mass 2M attained thereafter? (Cornell 2009) Homework Equations Not...
  18. Y

    I Effective electron mass of tungsten

    Hello! Please tell me what Effective electron mass of tungsten and Effective hole mass of tungsten?
  19. S

    Centre of mass of a hollow pyramid

    Question: Calculate the centre of mass of a uniform, square-based pyramid of height H and base length B (taking the centre of the base as the origin). Hence, or otherwise, derive an expression for the centre of mass of such a pyramid with a pyramid-shaped hollow cavity (of height h and base...
  20. R

    B Universe's Flatness: Mass, Gravity, Dark Energy Explained

    So, this is a bit of an odd question, but something I was curious about. I recently learned in layman's terms that the universe is considered flat because of how we measure triangles in 3D space, in particular the CMB. I've also learned that the cosmological constant that was derived from GR...
  21. S

    I Specifically, why is the neutron heavier than the proton?

    Proton is made of 2 up, 1 down quarks Neutron is made of 2 down, 1 up quarks The up and down quark have different masses, which account for some of the mass difference. I've also read that hadron masses depend upon the interactions/dynamics inside the particle, not just the quarks contained...
  22. Sebastiaan

    I Calculating Robert Zubrin's Dipole Drive Mass Flow

    I'm trying to understand calculation made Robert Zubrin in his presentation on Dipole Drive source: In here he made the following statement "A Coulomb of protons has a mass of 0.011 milligrams. If the jet power is 400 W, and the potential difference is 64 V, so the proton current will be...
  23. V

    Mass needed to balance the magnetic force on upper rod

    Homework Statement Two straight rods 60 cm long and 2.0 mm apart in a current balance carry currents of 18 A each in opposite directions. What mass must be placed on the upper rod to balance the magnetic force of repulsion? ## \mu_0 = 4 \pi * 10^-7 ~\frac {T * M} {A}## ## g = 9.81 ~m/s ##...
  24. R

    I Are Mass, Volume, and MOI Enough to Determine Dimensional Identity?

    I am looking to prove or disprove the following statement: Two objects, of the same homogeneous material, the same mass, the same volume, the same center of mass and the same moment of inertia will be dimensionally the same. If there is a way to generate a mathematical proof, that would be...
  25. S

    Vibration of a mass connected via preloaded spring

    The setup: I have a mass (m1)connected to a much, much larger mass (m2) via a preloaded spring. They start out in contact because the preloaded spring holds them together. Now suppose the large mass is subject to vibrations, possibly at the resonance of the structure. Will the two masses...
  26. Dante Meira

    Move a mass on frictionless surface in a vacuum chamber

    How much energy is necessary to move one kilogram of mass horizontally for one meter on a perfectly frictionless surface inside a vacuum chamber? Assuming the initial velocity of the mass is zero, the mass is at rest.
  27. P

    Mass suspended by bars in two configurations

    I have these two cases of a mass hanging from beams. The question is in which of the two cases will the mass travel the most distance in the vertical direction assuming we are in the elastic region. All i can think of is to calculate the tension for each of the two cases, Whichever case has...
  28. SamRoss

    I Still have questions about photon mass

    Just read the FAQ post "Do photons have mass?" and I'm still confused. The post says that all of the photon's energy is in the pc term of the energy-momentum equation. (1) But isn't p equal to mv, implying there is mass? (2) The post also says there is no inconsistency with E=mc^2 but doesn't...
  29. I

    I Invariant mass plots for resonance 'particles'

    The interaction p + π- → n + π- + π + may proceed by the creation of an intermediate 'particle' or resonance called a rho. This can be detected as a peak in the plot of invariant rest mass energy of the emergent pions versus frequency of pions observed. My question is quite simply, invariant...
  30. J

    I Which object will hit the surface of a planet first?

    If we have two objects A and B appear on the opposite sides of the equator of a planet like Earth with the same mass as Earth. Object A is a neutron star with the mass of the sun and object B is a iron cube with the mass of one gram. Will A or B hit the Earth at the same time or will one hit...
  31. Islam Hassan

    I Mass Equivalence of Photon Content Inside the Sun?

    If it takes anywhere between 5,000 to a couple of hundred thousand years (various internet sources have various values) for photons generated in the sun’s core to reach its surface and radiate out, what is the estimated mass equivalence of all these photons making their way out from the core to...
  32. dRic2

    Mass and energy balance equations for a tank filled with H20

    Hi, this problem should be very simple: I have a tank containing water. (going in and out). I want to write the differential equations to see what happen to the temperature and the level of the vessel if the flow of water is not constant. the system should be: $$A \frac {dl} {dt} = F_{in} -...
  33. A

    Thermodynamics problem -- Find the mass of water that vaporizes

    Homework Statement Find the mass of water that vaporizes when 3.02 kg of mercury at 223 °C is added to 0.347 kg of water at 83.4 °C. Homework Equations Mercury Q = Water Q + Water mL mc∆t= mc∆t + mL The Attempt at a Solution mass of vapor = ((3.02)(140)(223-tfinal) - (4186)(.347)(change in...
  34. S

    I How to Calculate Power of a Turning Shaft?

    Hello, can someone tell me how, or provide me a formula, to calculate the power of the turning shaft? in Nm or Watts, I don't mind. The mass (23Kgr) is turning at stable speed of 100 rpm by external independent force. The shaft is supposed to be on bearings both sides.. I made a picture to save...
  35. C

    I Distance between two nucleons

    The potential energy associated to the interaction between nucleons has its minimum (point of equilibrium) at ##r\sim 0.7 fm##, as showed in the following graph: Nevertheless, there are two facts that are, apparently, in contrast with this: - The average distance between nucleons is...
  36. Islam Hassan

    I If the Universe’s Mass was 100 At the Moment of the Big Bang....

    Supposing that the total mass + energy content of the Big Bang was 100 in energy-equivalent terms. What would we consider its energy-equivalent mass to be today? If the universe is today accelerating and that acceleration is not abating, then (naïvely perhaps...) its (dark-energy) potential...
  37. C

    I Pauli principle and coupling term in Weizsäcker formula

    Consider the pairing term in Weizsäcker formula. Here https://en.wikipedia.org/wiki/Semi-empirical_mass_formula#Pairing_term it is claimed that: I don't understand how Pauli exclusion principle should be the cause of this. This term comes from spin-spin interaction (or "coupling"), but I do not...
  38. R

    B 2 large objects of equal mass, Will they move each other?

    Suppose there are 2 planets the size (diameter) of Jupiter. Both have the exact same mass. They are separated by a distance of about 10 times the diameter of the planet. They are both at rest. Now, will they start moving towards each other or stay in the same place? This is a sort of thought...
  39. barryj

    Finding the Velocity of a Mass in Circular Motion

    Homework Statement See attached diagram and statement of problem Homework Equations Conservation of momentum ... mv = MV + mv/2 mv/2 = MV V = mv/(2M) centripetal force...centripetal force equals weight at top of circle. MV^2/L = Mg V^2 = Lg V = (Lg)^.5 The Attempt at a Solution Set V = V...
  40. prakhargupta3301

    Exploring the Relationship Between Velocity and Displacement in Pulley Systems

    Homework Statement Homework Equations xcxcxcxcxcxcxcxcxcxcxc[/B]The Attempt at a Solution My attempt: Let displacement of A be x m, Let displacement of B be y m, and Let displacement of C be z m. Step2: [/B]a+b+c+d=(a+x-y)+(b+x)+c+(d+z) 2x-y=-z Differentiating LHS and RHS components...
  41. A

    Gravity of the Earth if its mass were doubled

    What would be the value of gravity on the surface of the Earth if its mass was twice as large and its radius half of what it is now?
  42. L

    Center of Mass Balancing Question

    The question is: The orange and blue cat are currently balanced on the see saw. The orange cat then eats a bird, which of the following could make the see saw balanced again? - I attached the picture that the question is referencing. And the possible answers are: A. Orange cat stays at same...
  43. B

    Use triple integral to find center of mass

    Homework Statement Find the centre of mass of a uniform hemispherical shell of inner radius a and outer radius b. Homework Equations ##r_{CoM} = \sum \frac{m\vec{r}}{m}## The Attempt at a Solution Using ##x(r,\theta,\phi)## for coordinates...
  44. P

    Energy problem with 2 objects (a mass flying vertically off of a ramp)

    Homework Statement Consider a platform (mass: M) which horizontal surface AB s smoothly joined to vertical surface CD as shown in the figure below. Initially, the platform is fixed in place on a horizontal floor. A small object (mass: m) is placed on AB and given an initial speed of v in the...
  45. H

    Melting time vs Temperature and Mass

    I recently saw the movie “Man of Steel”. In Superman’s fight with Zod, Superman cuts (by melting) a steel I-beam, that Zod is about to hit him with, with a swipe of his heat vision. To melt steel that fast (under 3 seconds) requires a large temperature. My question is how can we calculate the...
  46. W

    2 weights on strings, 1 attached to pulley, the other end anchored

    Homework Statement https://imgur.com/jE8SMDR That's a drawing of the problem. I need to solve for the ? weight. Homework Equations not sure The Attempt at a Solution none, I don't want the answer, I just want the relevant equations. I haven't taken physics in a few years though (I'm out of...
  47. V

    An object of some mass, m, is accelerated upwards....

    Homework Statement an object of some mass, m, is accelerated upwards (from rest) off the surface off the Earth for some unknown time, t. At the end of this time, the object is traveling at some new speed, x. Derive the following formula. That is, show that no matter how much time the rocket...
  48. R

    Calculating the mass of an object

    Homework Statement A dog runs 480m in 28 seconds , we’ve to work out the mass of the dog Homework Equations F=ma [/B] M=f/a The Attempt at a Solution Really at a cross roads as every angle I work at this I need the mass of the dog to calculate the other components , a simple yes or no...
  49. C

    Length Contraction/Relativistic mass question

    Homework Statement The proper length of spaceship A is 60.0m and the proper length of spaceship B is 120.0m. The proper mass of spaceship A is 15000 kg. An observer on Earth watches the two spaceships fly past at a constant speed and determines that they have the same length. If the speed of...
  50. S

    Two elastic ropes, Acceleration and Height Problem

    Homework Statement As on the paper below: Homework Equations Suvat? The Attempt at a Solution As on my paper a) I think I got the acceleration correct by measuring the angle, halving the angle to get the force upwards by each rope. Or is that the wrong answer? b) Should be half as it’s...
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