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. Z

    B Coriolis problem - Point mass movement upon release from Earth

    If there was no atmosphere and a point mass was released at the 45th parallel and able to counteract the centripetal force of gravity (hovering 10ft off the surface), how long would it take before it ended up at the equator.
  2. Sabra_a

    Mass fraction and volume of a gas in a cylinder

    I have attached the full answer in PDF file. I'm not sure about the answers. will really appreciate if they get checked
  3. G

    To find the velocity of a mass attached to the midpoint of a spring

    Could I please ask for help regarding part (a) of this question: If I get part (a) then part (b) will follow. So, here's my answer to part (a): I'll be using the formula Elastic Potential Energy in a spring = (Yx^2)/(2a) Where Y is the modulus of the spring, x the extension and a the natural...
  4. lLehner95

    Find the photon energy in the center of mass frame and vice versa

    I tried to use the Lorentz transformation: ##E^{*}_{\gamma }=\gamma _{cm}E_{\gamma }-\beta _{cm}\gamma _{cm}p_{\gamma }## We have a photon, so it becomes: ##E^{*}_{\gamma }=\gamma _{cm}E_{\gamma }(\beta _{cm}-1)## Unfortunately, the solutions say that the correct way is to use the inverse...
  5. Alfredo Tifi

    I What if a body loses 86,6% of its mass as couples of gamma photons?

    After emitting two photons (or any other kind of energy) in the direction of motion and in the opposite direction, the velocity of the body (a big charged and unstable particle) remains unchanged, while the kinetic energy decreases. This entails a decrement of the rest mass, or of the inertia of...
  6. Santilopez10

    Mass attached to a rotating spring

    a) Our force can be represented as: $$\vec F= -k(r-H) \hat r$$ then the equations of motion are: $$\hat r: \ddot r -r {\dot{\theta}}^2=-\frac{k}{m_1}(r-H)$$ $$\hat{\theta}: r \ddot{\theta} + 2 \dot r \dot{\theta}=0$$ Plus we know that angular momentum is constant then $$|\vec L|=m r^2...
  7. Mimosapudica

    Calculating the power delivered when a block of mass m slides along

    Force along the horizontal would be T cos(theta) Frictional force (which is in the opposite direction )= μmg So net force in the direction of velocity = Tcos(theta)-μmg P= [Tcos(theta)-μmg]v But this is not so, the right answer is given to be Tvcos(theta). Why should we not consider the...
  8. Andrey Burian

    Is it possible to create mass on four springs (in Simscape Multibody software)?

    Dear Community, I just started to master Simscape Multibody and at the moment I'm trying to simulate mass on four springs. However, when I build parallel connections, the program writes an error, for obvious reasons, because the mass is tied to the spring, and when the spring moves, the mass...
  9. P

    B How Can Photons Contribute Mass to a Container?

    My question comes from reading the wikipedia page on mass-energy equivalence. The statement would seem to be contradictory: So photons contribute to the energy (and therefore mass) of the container; but photons are massless - that is, they have 0 rest mass. But doesn't this mean that we're...
  10. F

    How do we know the mass of an electron?

    I've been researching the proof of subatomic particles given the fact that we have never seen them before. It has always been recognized that protons, electrons, and neutrons exist; but I question how we know for certain they exist. Across my studying I've realized that in 1897, J. J. Thompson...
  11. X

    I Giving mass to other particles?

    Higgs bosons are very heavy particles (probably 1000 times heavier than a protons) and very unstable. Now we can create them in particle accelerators like LHC, like countless of other particles. But wait. This one can give mass to particles without mass, does this violate the conservation of...
  12. Kermit_the_Phrog

    Acceleration of a mass lowered by a motor (Help with Non-Ideal Pulley)

    Summary: Non - ideal pulley question, should be easy but has got me good Hey guys, looking for some help on this pulley question. It involves torque, and works with Newton's 2nd law in conjunction with a non-ideal pulley. Text of question: " When the motor in the figure below lowers the m =...
  13. F

    Estimate the mass of the water (Carnot cycle)

    m=Q/c(79*ln80)
  14. Like Tony Stark

    Prove that a mass has simple harmonic motion

    If I write Newton's equations, seen inside the room and with non tilted axis we have: ##x) N.sin(\alpha)-Fe.cos(\alpha)=m.a_x## ##y) N.cos(\alpha)+Fe.sin(\alpha)-m.g-f*=m.a_y## Where ##f*=ma##, ##Fe## is the elastic force. Then, how can I realize about simple harmonic motion? I also can think...
  15. Nimarjeet Bajwa

    How can we find the center of mass of a solid cone?

    is this method even possible? anyways here is my attempt Step1) y= 2H/3 ( H is the height of the cone) step 2) we take the density (ρ)= 3M/π R2 H. The problem i am facing is to Find "dm"
  16. S

    Conservation of energy: a mass and pulley system

    The solution is an application of the law of conservation of energy. Start with equation (1). The masses are in equilibrium and are not accelerating. This implies that ΔK = 0, because the kinetic energy will not change without acceleration. Thus, we are left to find equation (2) in terms of θ...
  17. M

    I Inertial Mass as Speedometer: Physics & Universe

    I get that the concept of relativistic mass has sort of been deprecated in physics these days and that relativistic momentum is supposed to be seen as more well useful. So let momentum equal ##\mathtt ~~ \frac {mv} {\sqrt {1 - \frac {v^2} {c^2}}} ~~## or ##~~{mv\gamma}~~##. So mass is supposed...
  18. N

    Velocity of an object with varying mass

    I have tried several things but I am a little uncertain if I’m thinking right so a little hint goes a long way. I think I have to use the law of conservation of momentum as the collision between the raindrops and the box is inelastic. But I am unsure how to set up the equation.
  19. A

    Is a loaded forklift more likely to tip over when its load is lifted?

    ?
  20. M

    Find the fractional increase in inertial mass when an ice cube melts

    Summary: Apparently an ice cube gains mass when it melts So I'm asked to "Find the fractional increase in inertial mass when an ice cube melts ". All I've got off the top of my head right now is that a cube has energy = mc^2, and then when the cube melts, energy Q = (Heat of fusion)(m) is...
  21. B

    B What Happens to a Dead Galaxy's Mass?

    Summary: Does the gravitational pull of a dead galaxy diminish? I have a question about dying galaxies. Most of the answers I've found thus far relate to them losing the ability to generate stars, or to general disbursement of mass caused by dark matter. This is not what I'm looking for. I am...
  22. W

    Symmetric top with constant charge to mass ratio in a magnetic field

    Setup: Let ##\hat{\mathbf{e}}_1,\hat{\mathbf{e}}_2,\hat{\mathbf{e}}_3## be the basis of the fixed frame and ##\hat{\mathbf{e}}'_1,\hat{\mathbf{e}}'_2,\hat{\mathbf{e}}'_3## be the basis of the body frame. Furthermore, let ##\phi## be the angle of rotation about the ##\hat{\mathbf{e}}_3## axis...
  23. S

    Solving for weight and mass in kg in an elevator

    Fn= normal force W=mg W=(65)(9.8)= 637N Fn-637= -(65)(0.2*9.8) Fn= 509.6N I got the weight of the woman in the elevator, but I have trouble finding what the scale reads in kg. I was given the solution which read: a = (g-0.2g)= 0.8g W= 0.8g*509.6N= 52kg. My questions 1. why do I have to...
  24. Meruem

    Force Needed to Push Bodies in Space: 100kg vs 1kg Mass

    Do we need more force to push a body with 100kg mass than of 1kg mass in space(in vacuum)?
  25. S

    How to calculate the centre of mass

    1) I'm not sure I quite understand this statement, is there an example that can be given to show this statement mathematically? 2) Is there any derivation for this equation to calculate position centre of mass below?
  26. Z

    A Effective mass of the electron for Si

    https://ecee.colorado.edu/~bart/book/effmass.htm#short Looks like the effective mass for holes in Si can either be 0.57 or 0.81, according to the link above. Is there a temperature regime where one effective mass should be used instead of the other? Is anyone able to explain in layman's terms...
  27. ValeForce46

    Pendulum with a mass on a container (thermodynamics problem)

    The kinetic energy of the pendulum ##K=\frac{1}{2}\cdot m\cdot v^2## will turn into heat (entirely). So both the air and the block of iron will change their temperature. To find ##n## (moles of the gas) I can use the ideal gas law: ##n=\frac{pV}{RT}=0.9 mol## Do I have the following equation...
  28. F

    B Relationship between mass and energy

    Great. I will be moving into general relativity next. Before that, I will touch on one more topic: energy and mass, a topic of special relativity, and the formula ##E=m c^2##. There is rest mass ##m_0## (the amount of stuff an object is made off, an invariant) and the inertial mass...
  29. Kaushik

    Moment of Inertia of a hollow sphere with Mass 'M' and radius 'R'.

    Homework Statement: Derive the formula for moment of inertia of a hollow sphere. Homework Equations: Required answer ##\frac{2MR^2}{3}## Consider a Hollow sphere. At an angle ##Θ## with the vertical, consider a circular ring whose moment of inertia is given by ##MR^2##. The most basic...
  30. jisbon

    Help Me Solve My Diagram Problem: Calculating Center of Mass

    Not sure what I went wrong here, anyone can help me out on this? Thanks. EDIT: Reformatted my request. Diagram: So as far as I know to calculate the center of mass for x, I have to use the following equation: COM(x): ##\frac{1}{M}\int x dm## And I also figured that to find center of mass, I...
  31. Ranku

    I Higgs Boson: What Gave Quarks & Leptons Mass?

    The Higgs boson with mass couples to quarks and leptons to give them mass. What was the nature of these particles before they acquired mass? Were they virtual particles?
  32. nmsurobert

    I Is Apparent Mass Loss Due to Air a Factor in Measuring Object Mass?

    We were discussing apparent mass loss in water in class yesterday. A student asked if apparent mass loss happens in water, does it also happen in air? And if it does happen in air then why do we not compensate for that when determining the mass of an object in air. I did some rough math trying...
  33. K

    Mass Transfer in a Binary Star System

    Homework Statement: A binary star system consists of M1 and M2 separated by a distance D. M1 and M2 are revolving with an angular velocity w in circular orbits about their common center of mass. Mass is continuously being transferred from one star to the other. This transfer of mass causes...
  34. A

    B Mass Defect: Is my understanding correct?

    Mass – Energy Relationship: According to Einstein’s special theory of relativity, when the energy of a body increases, so does its mass, and vice versa. If the difference in energy is indicated by ΔE and the difference in mass by Δm, these two quantities are related by his famous equation...
  35. Y

    Relationship of a planet's mass, size, and acceleration due to gravity

    Choice D is obviously wrong therefore leaving us with choices A, B, and C. Can someone explain the relationship of the three variables stated above (mass, volume, and acceleration due to gravity)? Thank you.
  36. Kaitlynn Robicheaux

    How Do I find Force when only Distance and Mass are given?

    I'm doing a lab for physics where I attach different weights to a spring and to measure different types of potential energy. I have already successfully completed the experiment using the virtual lab in the link below. I did three different trials using weights of 50, 100, and 250 grams. I...
  37. E

    A Future of the electron neutrino mass limits

    In five years also experiment KATRIN will give either the upper bound of electron neutrino mass (0,2 eV) or even the mass of the electron neutrino. https://www.katrin.kit.edu/ My question is, what we can expect from the astronomical and non-astronomical measurements to improve these data? I...
  38. Old-Alien

    A string attached to a fixed wall and a mass on a spring

    Hi all. Multiple part problem that I'm really stuck on. I'll attach a file. At first I had attempted the whole problem with the idea that fixed wall was a fixed point, and that the mass on a spring was a "free" point. But I learned later that the mass can't be treated like a "free" point since...
  39. Shivam

    Two balls of mass 4kg and 2 kg are moving in 1-D, answer the following

    My attempt- a) used equation { MV + mv = (M+m) V' } and got the right answer. b) I assumed that potential energy was asked for when the two balls were moving together with velocity 9.3m/s, so I used that when before the collision K.E( of m) + K.E( of M) will be equal to K.E(of M+m) +P.E(...
  40. Prabs3257

    Velocity of the center of mass in constrained motion

    I tried getting the velocity of a which by using constraint came out to be 3 and by using the eqn for vcom i got the ans as 3.5 i just want to confirm is this the correct answer
  41. J

    I Why don't strings have a Planck mass?

    I understand that strings have a size of roughly the Planck length ##l_P## of ##10^{-35}## m. If that is the case then one would expect that their mass would be roughly the Planck mass which is an enormous ##10^{19}## GeV. (Strings that have small spins, like standard model particles, are...
  42. JD_PM

    Implications of mass energy not being conserved for ##\beta^+## decay

    ##\beta^{+}## decay (a proton decays to a neutron + positron + electron neutrino) is a decay in which mass energy is not conserved. I've been taught that if that ought to be the case for a decay/reaction, it would be forbidden (please see solution manual below): But ##\beta^{+}## decay is...
  43. Physics lover

    EMF induced in a rotating rod having mass

    I first calculated induced emf and then calculated torque about O.But what will i do further.I think i need to find current and then fidn emf=IR. Help please.
  44. michael872940

    Can I determine mass & spring k from graph of wave, t, a, & vectors?

    Classical problems for hookes law generally give either mass or spring constant. What if I have a graph of a wavelike structure that is oscillating which I can use to measure for example: T (period), t (time), Δx (displacement), v (velocity), a (acceleration) and other variables is this...
  45. F

    I Is there a violation in logic when we define notions of mass and force?

    Which part of Newton's second law is definition and which part is law content?It seem that there is a violation in logic, because we define the notion of force through the notion of mass, then we define the notion of mass through the notion of force when we consider the second law.
  46. S

    Relation between mass distribution and angular velocity

    Is E the correct answer because I think angular velocity is independent of mass distribution of the object? Thanks
  47. dedocta

    I FRB's source as Rail and/or Coil Guns (or mass drivers)

    Summary: FRB's source as Rail and/or Coil Guns (or mass drivers) Hello, I've been studying rail and coil guns recently, and certain applications of this technology can result in some pretty high speeds with a significant amount of mass. I've been wondering if these FRB's could be a result of...
  48. A185

    Dynamics: A wedge, a mass, and two pulleys

    Problem Statement: In the arrangement shown in the figure, a block of mass m=2kg lies on the wedge of mass M=8kg.Find the initial acceleration of the wedge. Assume pulleys and thread massless and surfaces smooth. Relevant Equations: FBDs
  49. Kaushik

    A small mass on a wedge having a stationary circular track

    A small mass of ##m## starts sliding down a wedge which is having a stationary circular track on it. If ##M = 2m## and friction exists between the wedge and the horizontal surface. Draw the Frictional force vs Theta graph. How to draw the graph? Please HELP
  50. E

    Force equation: use mass or weight?

    I require to calculate acceleration of an object caused by a force of 100N acting upon it. The weight of the object is 0.5kg I'm using the equation F = m * a Is it correct to use weight of the object instead of mass in the equation. Will it yield correct results? Or would I need to calculate...
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