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. harry_thawne

    What is the relationship between mass and weight?

    What does it mean that the relationship between mass and weight is constant and proportional? I think I don't get it yet. The weight depends of mass, but at the same time depends of gravity, so if mass increase, the weight so does. But if we're on Earth we know that"g" has a value, therefore...
  2. Physics Dad

    How Accurate is the Initial Mass Function in Predicting Stellar Distributions?

    Assumptions: 1) The minimum stellar mass in this cluster is 0.1M⊙ 2) The maximum stellar mass in this cluster is 150⊙ First calculate the local stellar density constant (ξ0) for this cluster using eq 1: Having rearranged this equation and using the limits of the minimum and maximum stellar...
  3. D

    Not sure if I have the correct angle and mass for this sum of forces

    Balance the forces east-west: 3.5kg*sin45º + 4.2kg*cos30º - 4.8kg*sin30º - E*cosΘ = 0 E*cosΘ = 3.712 kg balance north-south: 2.8kg + 3.5kg*cos45º - 4.2kg*sin30º - 4.8kg*cos30º + E*sinΘ = 0 E*sinΘ = 0.982 EsinΘ / EcosΘ = 0.982 / 3.712 tanΘ = 0.2645 Θ = 14.8º ◄ E = 3.712kg / cos14.8º = 3.84...
  4. Adesh

    Oscillation of a boat in still water (Metacenter and Center of Mass)

    Let’s say we have a boat whose longitudinal axis is the y-axis (which goes into the screen in the figure below) standing upright in a still water . ##S## is the Center of Mass of the boat and ##C## is the Center of Mass of the displaced water.On ##S## lies the force ##\mathbf W##...
  5. Q

    A What is meant by the mass of a superfield?

    I'm specifically referring to these slides Supersymmetry - Holomorphy on pages 7 and 8. Why is the mass of the superfield defined as \frac{\partial^2W}{\partial \Phi_H^2} and why are the equations of motion \frac{\partial W}{\partial \Phi_H}= 0 and not \frac{\delta \mathcal{L}}{\delta \Phi_H}= 0?
  6. tanaygupta2000

    Lagrangian of a spring mass system

    I know that from the given problem, I need to find the expression for Kinetic energy, KE = 1/2 m [r(dot)]^2 and Potential energy, PE = 1/2 k r^2 So L = 1/2 m [r(dot)]^2 - 1/2 k r^2 Hence H = 1/2 m [r(dot)]^2 + 1/2 k r^2 I assume that the fixed length r0 is provided to find the value of end...
  7. A

    B Fundamental particles and mass quantization

    We know that the energy levels for electrons surrounding nucleus are quantized , only coming in discrete levels. When I see the standard model of elementary particles table I notice specific masses for each of the particles whether they be quarks or leptons or bosons like the higgs. I know that...
  8. archaic

    Rigid body rotation problem: Mass on a cord spinning up a wheel on an axle

    (I know how to solve the problem, that's not what I am looking for.) I have a problem with how I ought to understand the moment of inertia. The only torque I see applicable on the wheel is that of the tension, and so I think that ##I## should be ##m_{\text{point}}R^2##, without including all the...
  9. A

    Calculating Energy Ratios: Moving Mass to and from Earth's Core

    a) In the rough approximation that the density of the Earth is uniform throughout its interior, the gravitational field strength (force per unit mass) inside the Earth at a distance r from the center is gr/R, where R is the radius of the Earth. (In actual fact, the outer layers of rock have...
  10. T

    B Particle with negative mass inside a black hole horizon

    [Moderator's note: Spin off from previous thread due to topic change.] Just as an aside and not related to the OP, would a real particle with negative mass inside the event horizon follow the runaway motion? Would it be ejected?
  11. V

    Calculate the center of mass of a non-uniform metal rod

    I know that if they had the same density they would have the center of mass at 1,5 m. But now that they don't the center of mass will be shifted towards the part of the rod with higher density. they will have their center of mass where they have equal mass p1*v=p2*v now i don't know how to...
  12. wobblegobble

    Help with this problem about a mass oscillating on a spring

    A mass (M) is attached to a spring (K). Mass moves in a one dimensional plane (horizontally) 1) If mass M is initially at x=0, what is the minimum Work required to bring it to x=x0 ? PE ? 2) M is released from x=x0, PE when x=xo/2 ? KE ? 3) PE when x=0 ? KE ? 4) PE when x=-x0/2 ? KE ? 5) What is...
  13. M

    Finding the 'g-force' of a decelerating falling mass.

    Hey all, I need a reality check and verification on some work I have been doing. I feel as though I might be too close to the problem now and am missing something about this. It's also been a few years since I studied physics at University, so I'm a little rusty. Problem: An initially...
  14. Adesh

    An isolated object can rotate only about its center of mass

    I was talking to someone about the equilibrium of fluids and we reached at some stage where we had to prove that in an external field the translational forces add to zero along with moments (torques) should also add to zero. The first one was quite easy but during the discussion of second...
  15. E

    Calculating System Work and Displacement of Center of Mass

    <work done a system> a) w=5N*(0.4m)=2J I think this is right, but b) center of mass initial = ((0.5kg)(0.05m)+0.5kg(0.65m))/1kg = 0.35m center of mass final = ((0.5kg)(0.45m)+0.5kg(0.4+0.1+0.3+0.25))/1kg = 0.75m I'm not sure for this one... How can I calculate the displacement of the...
  16. E

    New unit of mass in a different system of units....

    I'm finding it slightly tricky to just get a hold of where to start. I try $$\text{m}\text{s}^{-1} = \frac{c}{3\times 10^8}$$ If we then set ##c = 1##, that would seem to imply $$3\times 10^8 = \text{s}\text{m}^{-1}$$For ##G = 1##, I might also write $$\text{kg}\text{m}^{-3}\text{s}^{2} =...
  17. D

    How the mass of a planet affects the evolution of life on that planet

    Summary:: Specifically, how Earth and life on it would have evolved if our planet was twice as massive but with the same composition of building elements? Could humans or sentient, upright walking creatures appear in the evolutionary scale in a twice as strong gravitational field? How that...
  18. Jshu

    Simple Harmonic motion calculation for a mass on a spring

    Im not sure how to find k if I'm not given a force or period.
  19. O

    Given these values, determine the mass of the Earth

    Honestly at a loss. Don't know where to start, what formulas to use. Any help would be greatly appreciated!
  20. S

    Calculate the Mass of Steam / Enthelpy

    Detergent: Volume = 20hl = 2000L 1L = 10^-3 m3 2000L = 2m3 Density: 1020 kgm-3 Mass Detergent: (2)(1020) = 2040 kg Detergent heat gain = (2040)(4.13)(80-10) = 589,764 kJ Detergent heat gain = steam heat loss 589,764 = m(2738-603)(100-0) Mass Steam = 2.76 kg 95% effeciency = 2.91 kg The...
  21. hagopbul

    Using the forth flotation technique to mass produce SARS-CoV-2 serum

    Hello All: i remember (and saw ) that the SARS-ncov-2 layers have hydrophobic and hydrophilic properties few weeks ago i was reading about forth flotation and it is a method to separate metals , but on low temperature could we use it to separate the spike protein and mix it with immune cells...
  22. Quark Effect

    I Explaining Time Crystals: Matter, Mass & 4D

    Can someone simply explain to me what are the time crystals? What are they built from (matter, do they have mass)? I cannot find a clear explanation of them. I just know that ordinary crystals are 3d, time crystals - 4d.
  23. I

    Infinite Square Well Expansion: Mass m in Ground State

    A particle of mass m is in the ground state on the infinite square well. Suddenly the well expends to twice it's original size (x going from 0 to a, to 0 to 2a) leaving the wave function monetarily undisturbed. On answering, for ##\Psi_{n}## I got ##\Psi_{n}## = ##\sqrt{\frac{1}{a}}...
  24. S

    How do I find the mass of an object without k?

    time/#periods=T= 30.58/10= 3.058 Displacement=.6m T=3.058 I tried to rearrange hooke's formula to k=f/x but f=mg and I don't have mass. Using the period formula is also hard because T=2π( √m/k) and I have neither m or k :/ Please help thanks.
  25. C

    Standing Waves Homework: A Tuning Fork, a String and a Hanging Mass

    Hi guys, so I am struggling on the Standing Waves concept. I understand that these are waves that move in place but I don't know how to attempt this problem. Can someone set me on the right track?
  26. S

    About acceleration and mass....

    Now, if I recall correctly, lighter objects with smaller inertia do go faster in terms of acceleration and farther than objects with heavier mass or inertia when the same force is exerted on them. But what about same accelerations? If a light object and a heavy object were to undergo the same...
  27. SEYED2001

    B Can we measure any two of the energy, momentum or mass simultaneously?

    I want to know between which two quantities of energy, momentum, and mass there is an uncertainty principle going on. Can I measure any two of those at the same time? If yes, which ones? Thank you in advance
  28. T

    I The existence of negative gravitational plus positive inertial mass?

    The term “negative mass” gets puts forth occasionally, and it’s definitions can sometimes be unclear. the topic I’m interested in is particles which have both positive inertial mass and negative gravitational mass. So far, what theories do physicists have of speculating on the existence of...
  29. S

    B Mass, Energy, and Space-Time: How Do They Interact?

    If I had two objects with the same mass, but one had more energy than the other, would it curve space-time more than the other?
  30. B

    Find the mass of this ion moving in a magnetic field

    I had started off by equating the magnetic force to the centripetal force, to find the mass of a single ion. Then calculated the mass of what 1 mole of that ion would weigh to identify what the ion is Hence the answer would be nitrogen (option C) as 1 mole of nitrogen weighs 14g Would this...
  31. SpaceThoughts

    Velocity calculation of an accelerated mass based on an increasing force

    A known force is doubling (egal) over a known distance, accelerating a mass. How do I calculate the final velocity of the mass at the end of the known distance , when the mass has doubled? I don't know the time. The mass is accelerated from 0 meter and from 0 velocity.
  32. George Keeling

    I Comparing Planck's Mass, Length, Time and Energy

    Sean Carroll gives the Planck's set of four dimensioned quantities: Planck's mass, length, time and energy. I wanted to compare them with actual things.\begin{align} m_p=\sqrt{\frac{\hbar c}{G}}&=2.18\times{10}^{-8}\rm{kg}&\rm{{10}^{7}\ E. coli}\phantom {100000000000000000000}&\phantom...
  33. LawH

    B Energy, Mass, Speed of Light: Can We Reach It?

    Hello everyone! Let's say that you were to attempt to go as fast as possible on a spaceship with the mass of an average car in an absolute perfect vacuum. What I am wondering is, that if you were to reach a certain speed, and stop applying energy to this imagined spaceship, would the spaceship...
  34. TutaTeacherAllan

    Where Is the Center of Mass in a Triangle with Unequal Masses?

    Figure 4 shows three point masses glued to the vertices of a massless triangle of side L=2.0 m. Two of the massess are m=0.75kg and the other mass is twice that value, as shown in the figure. The device is allowed to rotate about point A in a verticle plane about the centre of the larger mass...
  35. M

    Find the Lagrangian of this single mass system

  36. C

    What is the mass of the ruler moments? (Answer: 127.04g)

    The answer is 127.04g. I’m getting close but can’t get the answer. Using 9.81 for gravity, the force where the balance is is 2.10(58146)N As it is balanced 2.10N x 0.29m = W x 0.50m where 0.50 is the centre of mass That gives W = 1.22N = 124.5g?
  37. B

    Time period of a mass spring system

    I have attempted to draw a sketch of this but can't see how the data they gave me help to find time period This is what value I have ended up getting but I believe is wrong Much appreciated for any help!
  38. B

    B What are the different ways to create negative effective mass

    Also can negative effective mass be used as a replacement in a warp drive? Also what is the most realistic warp drive theory?
  39. neilparker62

    Insights An Introduction to the Generation of Mass from Energy

    [url="https://www.physicsforums.com/insights/an-introduction-to-the-generation-of-mass-from-energy/"]Continue reading...
  40. Deepesh

    Does Increasing Mass Affect the Natural Frequency of Vibration?

    My query here is, Suppose there is a 2 kg mass To oscillate it/vibrate it, it will take some force and it will have some natural frequency Now I increase the mass to 5 kg so to vibrate it, won't it take more force and so at the end, won't the natural frequency of the object increase? as its more...
  41. A

    Automotive Motorcycle: Flywheel mass and rear wheel torque

    Hello, I made this account to ask this question that I’ve been loosing sleep over. My question is say you have 2 identical motorcycles the engine the exact same and everything the only difference is the mass of the flywheel one bikes engine has a flywheel twice the mass as the other will the...
  42. xWaldorf

    Exploring Newton's 3rd Law: Mass & Reaction

    So there's something I'm missing when I think of Newton's 3rd law of motion. If all forces between two objects exist in equal magnitude and opposite direction, how is it that, for example, when I'm driving my car, the car "runs through" all the air molecules, and they seemingly don't exert the...
  43. PainterGuy

    B Time dilation, relativistic mass and fuel consumption

    Hi, Could you please help me with the queries below? Question 1: A GPS satellite is moving faster than the earth, for every day on Earth the clock on the satellite shows one day minus 7 microseconds due to time dilation due to special relativity. However, since the Earth's gravitational pull...
  44. xWaldorf

    Unraveling the Mystery of Mass and Acceleration

    So, this may be a really stupid question, and I strongly feel as though I'm missing something here. How can it be that objects of different masses have the exact same acceleration when mass is in fact resistance to acceleration? And then, if in (a vaccum) I throw upwards M and m ( a bigger and a...
  45. elderj

    How does mass influence energy transfer?

    Summary:: How does mass influence energy transfer? Can someone help me with this question? Thanks!
  46. Amik

    Spring force question with a mass suspended on a spring

    Fnet=0 kx-mg=0 k=mg/x=0,25*9.8/0.2=12.25 But answer is 25(And they use 0.1 instead of 0.2 Why?)
  47. R

    Engineering Mass Transfer in a wetted-wall column

    Please can someone assist me as this particular question seems to have me completely confounded?
  48. ari-anne

    Finding distance from velocity, force, momentum, mass, and time

    I solved a and b fine, I just don't know where to start c a) i=Ft i=change in p and p=mv so i=90=45v so v=2m/s b) same thing just using the other mass i=90=70v so v=1.3m/s c) v=d/t so 1.3=d/1.5 but that would be d=1.95 and the answer key says d=.96m
  49. L

    Velocity change under drag and other forces: small mass, large delta-t

    I am working on simulating the movement of small spherical objects under the influence of drag and a number of other forces that, at least for now, don't depend on the object's velocity. Normally I would sum up all these forces, including drag, to ##F_\Sigma## and update the object's speed...
  50. R

    I What is the Invariant Mass of Two Perpendicular Photons?

    I think since Esystem=(PsystemC)^2 + (Minvariant C^2)^2. Then the invariant mass of the system should be zero, but I am hesitated with this is it always the case that photon that travels perpendicular to each other have zero invariant mass
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