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. cheekyhouidini

    Mass of water given only power and density

    Cannot figure out where to start, apart from maybe something to do with specific heat capacity of water?
  2. S

    Distance traveled and period of a mass - spring - pulley system

    1. How will the motion of M be? I assume wire S is inelastic so will M move downwards but not in straight line? (I mean M moves downwards but because the left side of pulley is connected to S, it will be static and the right side of pulley can go down along the extension of the spring so its...
  3. C

    Graphing a spring mass collision with a wall

    Hi, I'm looking for help making a graph/model for evaluating the "bounce" of a mass behind a spring that collides with a wall. The setup would include one simple spring mass system that is attached to a wall, and another wall which is closer to the mass than the spring's free length. The mass is...
  4. E

    B The Missing Mass of a reaction

    Wikipedia says this about the missing mass of a reaction: I wondered where such an expression is coming from? The invariant mass of a system ##M##, in natural units, satisfies $$M^2 = \left(\sum E \right)^2 - ||\sum \mathbf{p}||^2$$ If anything, then the "missing" mass (which they also...
  5. mcastillo356

    Question about the quotient of the charge and mass of an electron

    hello Witch of these are certain sentences? a-\dfrac{e}{m_e}>\dfrac{H^{-}}{m_{H^{-}}}\cdot{1000} b-\dfrac{e}{m_e}>\dfrac{H^{+}}{m_{H^{+}}}\cdot{1000} The first accurate measurement of e/m was made by english physicist J.J. Thomson in 1897, who demostrated that the quotient charge-mass of the...
  6. DarkMattrHole

    I Mass distribution behavior of the singularities during black hole mergers

    When two BHs collide the resulting single BH bulges and contorts until it settles down to a stable state. 1) Does this mean that during this 'settling' period the mass internal to the merged BH is not (yet) a singularity, but instead two 'singularities' spinning down around each other in...
  7. P

    Find the tension in the string of this two mass system

    I know that it will probably execute something similar to circular motion. I thought of conserving momentum but I think there is an external force being applied due to the impulse which will prevent me from doing so. I know that once I find the tension it would become very easy to find the...
  8. C

    Using Effective Mass to find the accelerations of 3 masses connected by pulleys

    Since 2nd pulley accelerates downward with the same acceleration of m1, and because the string around pulley has a constant length, it must be that a2=−a1+ar and a3=−a1−ar, where ar is the relative acceleration between the pulley and m2. From the above 4 equations, we are supposed to determine...
  9. LCSphysicist

    Question about potential energy as a mass approaches infinity

    I was thinking, what would be the consequence if we wouldn't adopt the ro in the infinite, and i conclude that it would just irritate the accounts, with one constant more, am i right? Once what matter is the diference between the U, and no the U infact.
  10. S

    Refrigerant - mass flow, power, COP

    This is a past exam Q, I don't have the attached pressure enthalpy diagram. Q = 120kW Cp = Refrigerant enthalpy = I've looked this up, for ammonia enthalpy = 35.06 kJ / mol T2 = 5 degrees C = (5 deg C) (1100 kPa/300 kPa) = 18.33 deg C +273.15 K = 291.48 K T1 = 2 degrees C = (2 deg C)(1100...
  11. 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...
  12. Physics Dad

    Initial Mass Function Problem

    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...
  13. 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...
  14. 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##...
  15. 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?
  16. 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...
  17. 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...
  18. 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...
  19. 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...
  20. 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?
  21. 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...
  22. 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...
  23. 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...
  24. 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...
  25. 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...
  26. 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} =...
  27. 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...
  28. 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.
  29. 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!
  30. 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...
  31. 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...
  32. 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.
  33. 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}}...
  34. 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.
  35. 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?
  36. 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...
  37. 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
  38. 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...
  39. 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?
  40. 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...
  41. 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.
  42. 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...
  43. 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...
  44. TutaTeacherAllan

    Calculating the center of mass

    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...
  45. M

    Find the Lagrangian of this single mass system

  46. 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?
  47. 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!
  48. 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?
  49. neilparker62

    Insights An Introduction to the Generation of Mass from Energy

    Continue reading...
  50. Deepesh

    Mass and vibration frequency

    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...
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