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. jdawg

    Engineering Heat and Mass Transfer: Thermal Radiation Circuit

    Homework Statement 1.) A piece of bread (ε = 0.85) is being toasted in a toaster, as shown below. The heating element of the toaster consists of a wire 2 mm in diameter that is wound to approximate cylinders spaced 2 cm apart. This element acts as a blackbody. The housing for the toaster is...
  2. B

    A rod of length L and mass M has a nonuniform mass distribut

    Homework Statement A rod of length L and mass M has a nonuniform mass distribution. The linear mass density (mass per length) is λ=cx2, where x is measured from the center of the rod and c is a constant. Find the expression for c.Find the expression for the moment of inertia of the rod for...
  3. E

    Finding the Kinetic Energy using the mass, radius and initial KE

    Information Given:Zero, a hypothetical planet, has a mass of 4.2 x 1023 kg, a radius of 2.8 x 106 m, and no atmosphere. A 10 kg space probe is to be launched vertically from its surface. Question: (a) If the probe is launched with an initial kinetic energy of 5.0 x 107 J, what will be its...
  4. R

    A Mass of Higgs, W and Z bosons going to zero at high energies

    Hi Everyone! Hope everyone is really enjoying pushing the Physics frontiers! Really need some help here. In the Electroweak sector of the Standard Model, it is apparently the case that the success of renormalisation to remove the Ultraviolet Divergence relies on the fact that at high energies...
  5. F

    I Why doesn't a photon's mass increase to infinity?

    Pretty self explanatory really. If a photon has a mass (1.67 * 10^-27 kg), and it travels at the speed of light, why does it's mass not increase to infinity?
  6. Mr_Quantum

    B Exploring the Concept of Relative Mass

    Is the mass relative?
  7. A

    Relationship between mass and acceleration

    Hi. I am currently working on an assessed science experiment write-up. The experiment is about whether or not if mass of a pendulum bob affect the oscillation time for a simple pendulum. Obviously, the answer is no but I am struggling to write a concise and accurate explanation to why this is. I...
  8. A

    What Does Capital V Represent in Mass Balance Equations?

    Please tell me what capital V and v mean in this equation. And how can we derive the second equation from the first one.
  9. jdawg

    Heat and Mass Transfer: Nodal Networks

    Homework Statement So this is more of a really vague conceptual question, I'm sorry if it doesn't really make sense. I'm in the stage of learning this where I don't quite understand things well enough to form a proper question. I'm a little bit confused about nodal networks in heat and mass...
  10. M

    Finding the gas based off of mass

    Homework Statement Die average kinetic energy and impuls squared of a single molecule are: $$<E_{kin}>= 6.5*10^{-21} J$$ and $$<p^2> = 1.8*10^{-45} kg^2m^2s^{-2}$$ Which gas ist it? 3. The Attempt at a Solution ##\frac{m<v^2>}{2}=\frac{<p^2>}{2m}## ##\Leftrightarrow## ##\frac{<p^2>}{<v^2>} =...
  11. binbagsss

    QFT, Noether and Invariance, Complex fields, Equal mass

    Homework Statement Question attached: Hi I am pretty stuck on part d. I've broken the fields into real and imaginary parts as asked to and tried to compare where they previously canceled to the situation now- see below. However I can't really see this giving me a hint of any sort unless...
  12. F

    Center of Mass to lab-frame

    Homework Statement a) [Solved] What is the threshold energy in the center of mass for production of an antiproton in a proton-proton collision? Make sure quantum numbers are conserved. (This one was easy and I manage to solve it) b) In a fixed target experiment calculate the proton beam energy...
  13. Yan_Dalton

    I Why do objects with mass attract each other?

    In most cases, we know why things happen. Protons can stick with each other because of the strong nuclear force. There's all kinds of forces and we know mostly about why they occur and how they are transmitted. But I don't understand gravity. Why do objects with mass attract each other ? I know...
  14. N

    How to control the weight of an object?

    Hello everyone, First off, i would like to apologize for any spelling errors. I am Portuguese and my english is going to be very simple. I am in the process of building something and i am reaching out to the physics community for help solving a problem. I am a CNC programmer and while i was in...
  15. L

    What is the mass of potassium nitrate which crystallizes?

    Homework Statement 20g of saturated solution of potassium nitrate is cooled from 68 to 36 degree Celsius What is the mass of potassium nitrate which crystallizes? Potassium nitrate solubility per 100g of water 68 degree Celsius = 120g 38 degree Celsius = 60g Homework Equations I tried without...
  16. Suyash Singh

    What is the formula for calculating force using a spring balance?

    Homework Statement Homework Equations only basic school level physics will be needed in this question. The Attempt at a Solution The mass m1 pulls spring from first side and m2 pulls spring from the other side therefore reading should be m1-m2. But my answer is wrong. I can't understand what...
  17. D

    Light speed travel (now "understanding the difference between weight and mass")

    So an object unaffected by any gravity free floating in space has zero mass. Now could this object reach light speed. Or am I confused?
  18. Mr_Phil_Osophy

    Which forum should I post in for....

    Hi, I have a question about the bending of spacetime and its proportion and relation to the mass which causes the bending; and also how the bent space would interact with other objects as they come closer. I'm going to ask a more detailed question with some possible problems I would like to...
  19. N

    B Gravitation Mass & Proportional Gravity: Exploring Attraction Between Objects

    For all the theorists on gravitation, I would beg to ask a question on mass and it's proportional effect with gravity. IE :Greatest mass = Heaviest object. Simplistically, Why do objects with the highest mass become attracted to the nearest highest mass? Bowling ball falls to Earth via...
  20. Phantoful

    Damped harmonic oscillator for a mass hanging from a spring

    Homework Statement Homework Equations Complex number solutions z= z0eαt Energy equations and Q (Quality Factor) The Attempt at a Solution For this question, I followed my book's "general solution" for dampened harmonic motions, where z= z0eαt, and then you can solve for α and eventually...
  21. jybe

    Angular momentum changing as mass moves to center

    Homework Statement A 25kg child is spinning on a merry-go-round of mass 150kg and radius 2m at a constant angular velocity of 1rev/s. The child slowly walks to the center of the merry-go-round. Treat the child as a point mass and the merry-go-round as a uniform solid disk, and neglect friction...
  22. C

    How to calculate Fuel Mass Flow Rate

    I'm having a brain storm, If I have an 8 cylinder 4 stroke engine running at 4000 rpm over a 10 minute test and it consumes 4.4 Kg of fuel, then is the fuel mass flow rate as simple as the 4.4 Kg divided by the time to give me an answer on Kg/sec ? Thanks,
  23. Jan Nebec

    I Can we deal with relativistic mass once and for all?

    Hello! I've been reading about relativistic mass for last few days and it leads me to even more confusion. Supposing, we are assuming SR. 1. Why some people say that relativistic mass leads to confusion? As far as I learned, relativistic mass tells me the mass of an object, that is moving...
  24. jocarren

    I Does Rest Mass Change if c Varies?

    I'd like to ask an specific question. If c changes (for whatever reason*), does the rest mass of a given particle changes, asuming E is conserved? Let's say, for a given particle, the following initial condition: Placed in a vacuum**. Rest mass m0. Particle's energy E. Propagation speed of...
  25. I

    Forces acting on a spool of mass M

    Homework Statement Two forces ##F_1## and ##F_2## are applied on a spool of mass ##M##, moment of inertia, ##I##, and radius ##R## as shown in the figure. If the spool is rolling on the surface, find the ratio of forces, ##F_1/F_2## such that friction between spool and the surface is zero...
  26. HethensEnd25

    Fin/Fan heat exchanger mass and energy balance

    I am currently working on a project which requires a mass and energy balance on a fin/ fan heat exchanger. The problem I am running into is finding how to apply the fin efficiency to find out the amount of hea tbeing dissipated through the fins. The hot fluid is water and the cooling fluid is...
  27. Jan Nebec

    B Gravitational Mass & Velocity: Is There a Correlation?

    Hello! The equation for relativistic mass by special relativity tells us the relativistic mass for object in motion...but since inertia mass has same value as gravitational, does this formula also apply for gravitational mass? Thank you!
  28. vanhees71

    A Usefulness of relativistic mass

    [Moderator's note: This thread was spun off from a previous thread in the Quantum Physics forum. It was moved here since this specific subject is more on topic in this forum.] I didn't say that somebody who uses the relativistic mass doesn't understand relativity. It's just an unneeded...
  29. G

    Pure rolling of sphere having non uniform mass density ?

    in case of rolling without slipping of a solid sphere having uniform mass density the condition is Vcm (velocity of center of mass ) = Rω or [a][/cm] = Rα ,which comes from the fact that if an object that rolls without slipping the geometric center of the body travels 1 circumference along...
  30. diPoleMoment

    B Black hole emits quantum particles from the mass sucked in?

    So the Hawking radiation and the flinging of matter from the black hole, could this explain where all the matter goes? I am unsure of the theory for the second one, but if matter is broken to its quantum particles then why can't those quantum particles be in the Hawking radiation. Still very...
  31. fishin_kitten

    B Mass and Time Dilation: Causes and Effects

    Any idea why mass slows time down? More mass more time dialation
  32. R

    Calculating water pressure and the required mass of water

    Basically what I'm trying to do is calculate the amount of water it would take to generate a given pressure at the water tap. Or to put it more simply I'm trying to figure out where the water line is damaged, well more for fun then actually being practical. The water system is simply a well on...
  33. Ciaran H

    B Where does the increase in mass come from in fission?

    If energy is released during nuclear fission, why is the mass of the products (the two new nuclei and fission neutrons) greater than the mass of the original nuclei? In accordance to E=mc^2, shouldn't the release of energy result in the products having a lesser mass than the original nuclei?
  34. H

    B The relation between mass,higgs boson, and boson field?

    In school we learn that mass is made of the amount of particles within an object!. but then we have found something called higgs boson and boson field which is said to be responsible for an object mass. I have read how higgs boson and boson field work but I still don't understand how the higgs...
  35. C

    Finding the Mass of a Hanging Rope (Wave Problem)

    Homework Statement "...you were presented with a geologist at the bottom of a mineshaft next to a box suspended from a vertical rope. The geologist sent signals to his colleague at the top by initiating a wave pulse at the bottom of the rope that would travel to the top of the rope. The mass of...
  36. R

    How increased mass and drag affect speed

    Hello. I read an article about aerodynamics. http://www.cyclist.co.uk/in-depth/2873/fat-v-skinny-who-goes-downhill-faster I'm a little bit confused with this statement regarding mass, drag, and velocity: "When you increase the mass the speed increases by cubic function, whereas if you...
  37. M

    Understanding the Derivation of Relativistic Mass in Inelastic Collisions

    Hi guys, thanks for helping with this! I'm a little stuck with this question about the derivation for relativistic mass. 1. Homework Statement By considering the inelastic collision of two balls as perceived in different reference frames show that the relativistic mass is equal to the rest...
  38. lfdahl

    MHB A center of mass determined triangle: Find the angles of the triangle P_1P_2P_3

    Masses $m, 2m$ and $\sqrt{3}m$ are located at points $P_1, P_2$ and $P_3$ on a circle $C$ so that their center of mass coincides with the center of $C$. Find the angles of the triangle $P_1P_2P_3$.
  39. S

    Can there be any acceleration without mass?

    So, we know that force equals mass times acceleration. A force is needed to cause an acceleration. I am wondering though, is mass required for accelerations to happen? Why or why not?
  40. S

    Period of a mass spring system with 2 spring of same K(vert)

    A mass attached to a spring is oscillating in Simple Harmonic Motion. If an other spring of same sprinc constant is attached parrallel to the other spring, what is the period of this new system (as a function of the initial period). Here's what I did and have no idea if this is right: For the...
  41. K

    Charges of ions in a mass spectrometer

    Homework Statement In a mass spectrometer, a few 126C ions are deflected with a radius of 12.9 cm. The ions have a speed of 5.67*10^4 m/s when they enter the field. The magnetic field has a strength of 3.2*10^-2 T. The charge of these ions must be ... SOLUTION: We use the formula: i F=qvB =...
  42. A

    I Chandrasekhar Mass and the Relativistic Star: Finding the Value of K for n=3

    From the mass radius relation I have gone through mass of a relativistic star ( polytrophic index 3) which is 4piM3(K/piG)3/2 can anyone please suggest me any information of where the value of k is determined for relativistic star( for n=3) via any link Where k is constt
  43. T

    Center of mass of a disk with a hole

    Homework Statement We have a circle of radius 4 with center at the origin of a referential, and a circle hole in it of radius 1 and center at (-2,0). We're supposed to calculate the center of mass. 2.MY QUESTION. I know, by the usual formulas for calculating center of mass I get 2/15 as the x...
  44. Richie Smash

    Calculate the velocity of a body with twice the mass to have the same KE

    Homework Statement A body of mass m, moves with a velocity v, and has a certain kinetic energy. What velocity would a body of twice the mass have to move to have the same kinetic energy. Homework Equations K.E=1/2mv2 The Attempt at a Solution I made an equation 2m1/2*v12/2= m2v22/2 from here...
  45. R

    Is it possible that the force on a body is zero when its mass is zero?

    Homework Statement :[/B] Ok, so my exams are coming and all sorts of crazy thoughts are banging my mind and now I have a question regarding a very simple law of physics, the funniest part, this is my last month of high school life...so at this juncture of life, i am having this crazy question...
  46. Nick tringali

    Is the Law of Conservation of Mass Always Obeyed?

    Are the laws of conservation of mass always obeyed. in a nuclear reaction mass is converted to energy therefore mass isn't conserved. I understand that energy is always conserved, but I feel like mass isn't.
  47. Michael Koch

    Wanted: Instructions for Leybold PGA 100 mass spectrometer

    I have a Leybold PGA 100 mass spectrometer, including the instruction manual. The instrument is paired with a gauge head. If either the instrument or the gauge head is exchanged, then an alignment is required. It's mentioned in the instruction manual there exists a supplement, which contains the...
  48. Gene Naden

    I Mass of Bound Particles & Mass-Energy Equivalence

    I am confused about the mass-energy equivalence relation as it applies to nuclei and nucleons. For nuclei, I read of a "mass defect." Naively, I supposed that since it is a collection of nucleons bound together, it has a negative binding energy and this is the reason for the term "mass defect."...
  49. Humbleness

    Calculating mass of a planet (Law of Universal Gravitation)

    Homework Statement You are on a deep space mission to search for Earth-like planets. Your crew locates a possible planet and with scanners finds the radius to be 7.5 x 106 m. A team lands on the surface. There, they hang a 1.0 kg mass from a spring scale. It reads 8.5 N. Determine the mass of...
  50. S

    I Mass Attenuation coefficient greater than 1

    Hello everyone, I don't seem to understand why mass Attenuation coefficient is greater than 1 at low energies where photoelectric effect is dominant. 5.2 cm^2 /g at water for 10 kev incident photons. Since it is the probability to interact per g of water how can it be greater than 1? I...
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