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. S

    Equations for a mass falling to Earth from a distance

    I have a question : If we consider the change in g due to distance from the Earth core; then y=distance from earth’s core t=time G=gravitation constant M=Earth’s mass k=GM $$y^2(t)=\frac{k}{y(t)^2}$$ If we consider air resistive force as proportional to speed squared, then: m=falling object...
  2. H

    Where did I go Wrong? Solving for Particle Speed with Mass & Charge

    F= 9*10^9 (5*10^-9)^2 / (0.05)^2 a=F/m = F/(3*10^-6) v^2 = u^2 + 2aS = 0 + 2a*0.03 v = 60 Where did I do wrong? Thanks!
  3. J

    Equilibrium: Mass on an inclined plane held by a string, find the tension

    6.2(9.8)=60.8 (incorrect) 46.2cos40.4= 35.2 (incorrect)
  4. D

    Lagrangian of a mass bewteen two springs with a pendulum hanging down

    What I first did was setting the reference system on the left corner. Then, I said that the position of the mass ##m_2## is ##x_2##. I also supposed that the pendulum makes an angle ##\theta## with respect to the vertical axis ##y##. So the generalized coordinates of the system would be ##x_2##...
  5. jovanovic_oliver

    B Understanding the Mass of Solar Wind and its Impact on Earth's Surface

    According to wiki sources "The average mass ejected is 1.6×1012 kg" I would like to know, what part of that falls to surface of the Earth?
  6. J

    Tension in a rope holding a mass under a helicopter rising at constant speed

    Helicopter lift weight of 500kg ,weight is connect with load cell to meassure tension. Neglect aerodynamic drag.. If helicopter accelarate up ,tension is rope is greater than 500kg. If helicpter accelarate down ,tension is rope is less than 500kg. If helicopter fly up with constant speed...
  7. I

    Find the mass of the Sirius system

    I'll be focusing on mainly trying to find a way to solve part a, as I don't actually know how to account for the tilt. When they said degrees arc I assume they're just saying degrees, so I found the distance of Earth to sirius to be around 1.50 x 10^8 km(radius of the earth), because of the...
  8. C

    Single degree of freedom system/equivalent mass

    It's possible to use Comsol to model a simple truss and the resulting frequency response looks like a single degree of freedom system. Using that data you can calculate a value for the spring constant, damping, and equivalent mass of the system etc and plot the frequency response of an ideal...
  9. I

    Time for a mass to land on another mass

    Originally I had thought this was a normal question and simply did the normal s = (1/2)at2, which got the answer of about 0.4s. The answer is however 0.9s, so I double checked the diagram. The right tail of M is tied to the string connecting m, and two strings connects the top of M to the...
  10. Helena Wells

    Pulley's mass is invariant to the physics problem?

    I have this system of masses and the goal is to find the velocity of $m_1$ at the ground. But it gives me the moment of inertia of the pulley as well which is $xMR^2$. I know how to solve a pulley problem but since it gives me the moment of inertia of the pulley maybe it has something to do...
  11. R

    B Dark Matter -- Is it possible that Dark Matter has Planck mass and Spin two?

    Is it possible that dark matter has Planckmass and Spin two?
  12. I

    Acceleration of rising mass and tension in cord

    First I determined the direction the masses will be traveling by comparing the change in potential energy, so when M2 rises by Δy, M1 drops by Δy. Potential energy decreases when M1 drops and M2 goes up. Tension force for string pulling against M1= 400 x gsin30°, and since there are two strings...
  13. K

    How to solve spring mass damper system manually?

    The other day when I solved a spring mass damper system in Matlab, I was curious how in olden days would have people solved the equation. We all know the 2nd order differential equation of the system: However if I know the time, damping coefficient, stiffness and mass, will I be able to find...
  14. J

    Confused about a 3 mass coupled oscialltion

    So the textbook uses 3 equations for these, d 2/dt2 (y1 + y3 − √ 2y2) = − k / m (2 + 1/ √ 2 ) (y1 + y3 − √ 2y2) d 2 /dt2 (y1 + y3 + √ 2y2) = − k / m (2 − 1/ √ 2 ) (y1 + y3 + √ 2y2) d 2/ dt2 (y1 − y3) = − 2k / m (y1 − y3) Now the question is asking for the largest natural frequency. Now I...
  15. J

    Damped Oscillation Amplitude Decrease vs. Mass Relationship

    so what I did was e^-(1/10.1)=0.9057 and e^-(1/14.8)=0.93466 Then 0.93466/0.9057 = 1.03198, so the heavier mass dampens 1.03 times more than the lighter mass. If the lighter mass decreases the oscillation to 72.1%, then the heavier mass would be 72.1%*1.03198 = 74.4, but this is wrong. It...
  16. duchuy

    Point mechanics -- Tension in a rope from a hanging mass

    Hi, I'm being asked to determine the tension of a rope only knowing that g = 9.8 m.s-2. I understand that in order to calculate tension, I would need to multiply mass with acceleration. But i don't understand how i would in this case. This is the question for reference. Thanks for your help...
  17. Norashii

    Calculate the center of mass of a deformed hollow cone trunk

    I couldn't make progress in this problem, I would appreciate some suggestion on how could I attack this problem. Thanks in advance!
  18. S

    Can we write mass in coefficients of elements in a chemical equation

    let's take a chemical equation - CH4+2O2 ------> CO2+2H2O From Reactant side- the coefficient of CH4 is 1 and the coefficient of O2 is 2 From Product side - the coefficient of CO2 is 1 and the coefficient of H2O is 2 we can write this chemical equation in terms of molecules,atoms,moles. Can we...
  19. O

    Millikan Experiment Based Marble Mass Homework

    I arranged the masses in ascending order: 11.0 g 11.1 g 20.6 g 21.4 g 21.5 g 25.7 g 25.8 g 25.9 g 31.6 g 31.9 g I found the average mass of the marbles: 22.65 g I found the difference in masses of the marbles: 0.1 g 9.5 g 0.8 g 0.1 g 4.2 g 0.1 g 0.1 g 5.7 g 0.3 g I found the average of the...
  20. shintashi

    B Mobility in a Strong Gravity Environment vs. Moving Mass?

    This is a basic conundrum that has bothered me for years: if you or a species like you is "adapted" to Twice Gravity (or any other multiple of 9.8m/2 squared) and your life functions and capacities are near identical, How strong/fast are you? Compared to 1G? See, this is the issue of mass vs...
  21. J

    Harmonic Motion of a Mass between two springs

    So first I found the total energy of the system by calculating the potential Energy, Ep=0.5k(l^2+l^2) and get 2.0475 (this part is right). Then I find w using the period T=2pi/w, so w=2pi/1.21=5.1927 I also found the amplitude using E=1/2kA^2, so A=sqrt(2E/k)=0.212132 Now this is the part I...
  22. JGHunter

    Lavoisier's Law of conservation of mass

    Hi, I'm writing a short story which addresses an issue in time travel that I don't really see getting addressed, and I was wondering where I could find the original quote where it is written that mass or energy can neither be created nor destroyed? I'm aware the original won't be in English...
  23. M

    Mass correction in ##\phi^4##-theory

    Before I start, let me say that I have looked into textbooks and I know this is a standard problem, but I just can't get the result right... My attempt goes as follows: We notice that the amplitude of this diagram is given by $$\begin{align*}K_2(p) &= \frac{i(-i...
  24. E

    I Source of Gravity of heavy mass as per GTR

    Regarding the equivalence principle of GTR, inertial mass and heavy mass are comparable, and are causing identically effects on mass objects. The pseudo force of inertial mass could be experienced in an accelerated frame of reference. In that point the "Force" appers, while energy is...
  25. Kaguro

    Angular momentum of orbit from orbit parameters and mass of sun

    L = mvr = mr (dr/dt) = 2m*r*(dr/dt)/2 = 2m*(dA/dt) So, A = (L/2m)T so, ## L = \frac{2 \pi a b m}{T}## Now, ##T^2 = \frac{4 \pi^2}{GM} a^3## So from all these, I get ##L = \sqrt{ \frac{GM m^2 b^2}{a}}## But answer given is ##L = \sqrt{ \frac{2GM m^2 ab}{a+b}}## (This, they have derived from...
  26. V

    What happens when the maximum is exceeded in the Mass-Spring System?

    If M is displaced by an amount + x from equilibrium.What happens to the two masses at the point of release for displacements of x and less? Will they remain static because mass m provides whatever it takes to stop mass M from moving till some x where m slips and M oscillates or Will they...
  27. V

    Find the tension of a rope with a mass and spring attached

    I'm having trouble with this problem, I think I solved it but I don't know if what I did is right... At first when the velocity is 0 and the spring is at its natural length, there's just gravitational potential energy, so $$E_i=mgh$$ And then, when the mass is released and then reaches its...
  28. A

    B Understanding Mass Excess and Atomic Mass in Nuclear Physics

    I see this term comes up in KAERI table and elsewhere. Now let me guess here and tell me whether I'm correct. The only element whose atomic mass expressed in AMU is exactly a round number is C12, for all other elements it's either bit more or less so in order not to have to write long numbers in...
  29. T

    Does change in 'g' affect frequency of mass spring system?

    I attempted using f = 1/(2pi x sqrt l/g) For Earth I found the value of length to be 0.0276m. Then I substituted the value in the equation, putting (1/3)g instead of g, to find the value of f in Mars. My answer is C. I am confused. Please help me.
  30. mtuck

    Relativistic Mass in this fission decay

    I'm not sure where to start
  31. R

    Find the Center of Mass for each of these figures

    hi I am struggling with simple question i need to find the mass center for each one :
  32. chem_

    Band theory: effective mass and Hall's coefficient

    Consider the following scenario. A material has the E-k band scheme as shown in the figure (extended scheme of zones). Could anyone give me a suggestion regarding the following : Electrical character of the material with the temperature. Sign of the Hall coefficient. Sign of the effective mass...
  33. B

    Solving 1D First Order Equations for 3D Mass Positions and Velocities

    Okay so I need to find 12 one dimensional first order equations that describe the position and velocity of both masses in 3 dimensions. The equations for the second body will be easy once I figure out how to do the first body, so I'll ignore that for now. For the first equation, I can rearrange...
  34. J

    Equilibrium Forces: Force to Move a Mass

    So I already know the normal force is 268.08 from a previous part of the question. I thought that the friction force must be less or equal to uFN for an object to stay in static equilibrium. So Tcos(angle)=uFN T=uFN/cos(angle)=116.49 But the answer is suppose to be 133.37.
  35. E

    Two rotating masses balanced by a third mass (rotational dynamics)

    Here's a diagram of what the system looks like: So far I have figured out what the initial angular velocity is, if the system is balanced (no movement): ## \sum F_m = m*\frac{v^2}{R_0}-\frac{Mg}{2}=0 ## ##m \frac{v^2}{R_0}-\frac{Mg}{2}=0 ## divide both sides by m ##\omega_0 =...
  36. J

    Conservation: Mass Dropped onto a Spring, Find the Compression

    First I wanted to find the kinetic energy the mass had when it hit the spring (converted from the potential Energy it had) thus Ek=mgh=9.8*2.6*3.5=89.18 Now I know as this Ek changes to 0 the potential energy of the spring as its being compressed will be at its maximum so, Ek=Ep...
  37. iVenky

    B Mass Reduction in Combustion: Real or Myth?

    I have studied in high school that all chemical reactions obey conservation of mass, as the atoms are merely re-arranged, but when I read through special relativity, I was reading that you can show an infinitesimal change in mass (based on E=mc2) in combustion that's not noticeable that's being...
  38. J

    Angular Momentum: Spinning Mass

    First I calculated the momentum of m1. Since m2 was at rest after the collision, all its momentum was transferred, so m1 has a momentum of 158 i hat. L=r x p, so its 916 k hat. This would also be the change in L because it was initially 0 when m1 had no velocity, so I know this is the net...
  39. lola1227

    Forces Experienced On Moon and Earth - What is the mass?

    So, I decided to do Fg=ma I tried 25(9.8)=1.62m m= mass However, when i did it i got a mass of 151 but when i put it into its separate equations, the fg is not 25x larger so fg=ma fg=151(9.8) = 1479.8and then fg=ma fg=151(1.62)= 244.62 but 1479.8/244.62 is not 25 it ends up being 6.05...
  40. bieon

    Pendulum, Rotational Inertia and Center of mass

    This is the figure given. My Attempt ##T=2\pi \sqrt\frac {I}{0.5gd}## ##\frac {m_r} {l} ## ##dm= \frac {m} {l}dx## ##dI = dm_r x^2## ##dI=(\frac {m_r} {l}dx)x^2## ##I= \int_l^0 (\frac {m_r} {l}dx)x^2 \, dx ## ##I_c.m=\frac {m_r l^2}{3}## ##I_,, = \frac {m_r l^2}{3}+m_p x^2## Given...
  41. PolVD

    Solve 2D Asteroid Problem: Step-by-Step Guide

    Hi everyone! I don't know how to solve the next problem, and if anyone could explain to me step by step how it is solved I would thank you a lot. I know it's not hard, but I'm not seeing how to do it. Thank you in advance!
  42. cwill53

    Integrating Mass of a Hollow Sphere: Multivariable Calculus Explained

    I know some multivariable calculus, I just want someone to walk me through the integration deriving the mass element dM and the integration of thin rings composing the hollow sphere. It would also be nice if you could show me doing it one way using the solid angle and one way without using the...
  43. A

    MHB Does Increasing Mass Reduce the Amplitude of a Forced SDOF Oscillator?

    I'm working on a forced single-degree-of-freedom (SDOF) oscillator. I'm trying to find how an increase in mass will affect the response amplitude? I'm looking for mathematical proof explaining this reduction in amplitude. How to derive \delta x
  44. K

    Finding mass to resonate a system

    My first step was to calculate Torques acting on system, I found 3, one given(external): a)torque produced by point mass: (m2)grcos(θ)=(m2)gr b)torque produced by spring krsin(θ)rcos(θ)=kr2θ c)external torque τ_o(t)=10sin(20t) I also calculated moments of inertia I=m1r2+(1/2)m1∗r2 then I...
  45. Mimi3616

    Changes in Work done with changes in the centre of mass of a tool

    Work done if centre of mass is away from us will be less. But how? Or should we consider torque?
  46. T

    Friction between a mass and a conveyor belt (ENGAA 2017)

    Please scroll-down to Q50: https://www.undergraduate.study.cam.ac.uk/files/publications/engineering_s1_qp_2017.pdf The correct answer is 'B', or 'mgsin(Θ)'. I put 'E', or 'μmgcos(Θ)'. There are unofficial worked solutions which I have been referring to when I have attempted the question and...
  47. virgil1612

    B Relativistic Photon Mass: Can It Exist?

    Photons have 0 rest mass. But could I talk about relativistic, or dynamic photon mass, that would be the solution of hf = mc^2 ? The relativistic mass would be m = m0/sqrt(1-v^2/c^2), where m0 is the rest mass, so 0, and v = c, so the denominator is also 0. The previous equations would give 0/0...
  48. patric44

    Proof related to the center of mass

    hi guys in the proof of the parallel axis theorem this equation is just put as it is as a definition of the center of mass : $$\int[2(\vec{r_{o}}.\vec{r'})I-(\vec{r_{o}}⊗\vec{r'}+\vec{r'}⊗\vec{r_{0}})]dm = 0$$ is there is any proof for this definition ? and what is the approach for it
  49. wcjy

    Mass with small charge sliding down a ramp

    When the mass starts sliding down, it will induce a current due to the cutting of B field. By fleming right-hand rule, the B field points into the field, charge going in the direction down the ramp (current pointing down the ramp?), therefore the force should be in the same direction of normal...
  50. MagneticNeutron

    Semi-Empirical Mass and E=mc^2 close, but both off? Binding Energy calc

    Hi, I am calculating the binding energy of 11- Na- 18 Stats: Table of nuclides has BE/A = 6.202276 ± 0.006249 MeV m used = 18.026878252 amu E= mc^2 answer = 5.894327537620224 MeV Semi Empirical Answer = 5.919667778950925 MeV Including excess mass in E = mc^2 method 1 - Calculate...
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