Mass Definition and 1000 Threads

So ##T+U=\frac{1}{2}m(\dot{x}^{2}+\dot{y}^{2})-mgy=constant##. If I derive this with respect to ##t## $$\dot{x}\ddot{x}+\dot{y}\ddot{y}-g\dot{y}=0$$ Then I use ##\dot{y}=\dot{x}\frac{dy}{dx},\ddot{y}=\ddot{x}\frac{dy}{dx}+\dot{x}^{2}\frac{d^{2}y}{dx^{2}}## to get...

I don't really know how to begin this problem. I need some advice

The center of mass of someone's thigh, shank, and foot are located at the following coordinates: Thigh: (2.7, 3.2) Shank: (2.1, 2.5) Foot: (1.5, 1.9) If the masses of them are respectively 9.6, 2.9, and 0.9 kg, where is the location of the entire leg? ANSWER: CM = (2.5, 3)I'm having trouble...

Problem Statement: How to calculate minumum angular velocity of a mass on a spinning plate Relevant Equations: f=mrw^2 Hi, here's the question: a) A rough horizontal plate rotates with a constant angular velocity of w about a fixed vertical axis. A particle of mass m lies on the plate at a...

How far will the spring extend, given that the block is not attached? Will it extend beyond its natural length? How to calculate at what point the box comes off the spring?

Dear all, I am back with another Spring problem. I have tried to use the insights I gained from your help last time: https://www.physicsforums.com/threads/find-v-x-of-a-mass-suspended-from-a-spring.972942/page-3#post-6190934 I figured I start with calculating the new equilibrium by ## x...

I was talking to a physicist who said to me that virtual particles can have a mass of a constant times by i ,as in the root of -1. I have been thinking about this more and it intrigues me. I have done some research into this and can't find further details. If they have an imaginary mass does...

What would happen if a black hole made entirely from anti-matter merges with another black hole made from normal matter? Since most of the product left over from the annihilation is in the form of light (gamma rays) would the black hole lose mass?

Problem Statement: NA Relevant Equations: NA Come across the mentioning that some particles have "no mass". Is this stated by physicists because there simply isn't evidence to prove that they have mass. It doesn't seem logical to make a fact based on absence of information to the contrary...

The red dots show the CM of each block. ##x## is the amount by which the upper block overhangs the lower block. The blue (dashed) line shows the CM of the combination. For maximum overhanging, this line lies on the edge of the table below. By symmetry, the CM lies exactly midway between the two...

Hi all, I'm trying to solve a problem of finite square well for the ##s## states graphically. The task is to find energy levels and wavefunctions of proton in a spherically symmetric potential, first for deuteron then ##^{48}Ca##. What makes me confused is the mass. For deuteron, the mass used...

Dear all, For an assignment, I am trying to find the relationship between the Sherwood number and the Reynolds number in a channel for different laminar velocity profiles, where there is a concentration of a species at both the top and bottom wall which is transported to the fluid. For this, I...

Suppose there is a photon with momtum p=h/lambda moving in the positive x-direction. Suppose it collides with an electron at rest and is completely absorbed by the electron, and that after the collision, the electron moves to the right with the same momentum of the photon. This seems...

I don't know in which category this subject belongs to. Anyways, here it is: https://www.sciencealert.com/a-new-study-backs-up-claims-that-sound-waves-really-do-have-mass-after-all?fbclid=IwAR2Cmsxm_Garm0PVn03f4UxVQ8adcK4Il3A_N7bUbJT1KaGR1ZfCbGuWVLE How exactly is this measured? Can we expect...

This is based on "Concept Question 10.4" in Andrew Hamilton's General Relativity, Black Holes, and Cosmology. I have modified the question somewhat in order to focus on what seem to me to be the key issues. Suppose we have a spherically symmetric ball of stress-energy surrounded by vacuum. More...

I am reading Tipler & Mosca 5th edition. On pages 289-290 there is an example problem which seems to assume that Newton's second law for torque works just as well when we apply it to the centre of mass of an object. However, before this example problem was introduced, the authors did not state...

In an accelerator when you're pushing/pulling a charged particle with a field that travels at the speed of light why should we expect to the particle to exceed the speed of light.

In the book by Tipler & Mosca, the section on F=ma for variable mass derives the following equation: ##\mathbf{F}_{ext}+\frac{dM}{dt} \mathbf{v}_{rel}=M\frac{d\mathbf{v}}{dt}## where ##\mathbf{F}_ext## is the external force on the system as a whole (ie not just the variable mass sub-system...

I am stuck, please help. I did the conservation part but then i can't move on.

Hi, so I was able to solve this problem by just equating the forces (Tension, mg, and EQ). But I thought I could also solve this problem with Conservation of Energy. However, I calculated it several times, and I never get the right answer this way. Doesn't the Electric Field do the work to put...

A ballistics-esque question. Suppose we are driving at ##x \text{ m/s}## and we have to suddenly brake. For students in driving schools they are told something along the lines of "during the braking, the body experiences ##y \text{ kg}## of force" or "the mass of the body is much higher than at...

My current understanding is that a person falling toward the surface of a planet with no atmosphere, would feel no force acting upon themselves even though they are accelerating relative to the planet. If the mass of the planet suddenly tripled while the person is in free fall, would the person...

I am labelling this as undergraduate because I got it from an undergraduate physics book (Tipler and Mosca). The uniform semicircle has radius R and mass M. I am getting the wrong answer but I can't see where I am going wrong. Any help would be appreciated. My solution: The centre of mass...

For bound system to form it must radiate away binding energy. By mass energy equivalence mass of the bound system is reduced proportionally to amount of binding energy. The question is from which mass this "binding mass" is subtracted. Common answer that I have seen is that this binding mass is...

My best estimate was to find the water height and assume it remains constant when venting the air. I know the initial weights of vapor and liquid ( I know the total mass of substance inside the vessel), so I find the new density of water and vapor and calculate the "new" mass and take the...

For some work of mine i need the plasma resonance frequency for tin nanoparticle, i searched various research papers and found different efffective masses tin for different orbits. here i attached screen shot from W A Roger and S B Woods (Cyclotron effective masses in white tin). What value is...

I have a feeling some integration will be required, I just want to see if anyone know of a quick way.

Could anyone kindly kind me as to where this formula is derived from and how, because I searched and can't find it anywhere

I am new to Simulink and I wanted to start practicing using a spring mass damper system. My first tutorial was this: Later, I wanted to model a spring system where a mass moving at a known velocity hits the spring. The governing equation and a similar modeling method given in the previous...

Summary: Does an atom in an excited state have a higher mass than when in its ground state? Summary: Does an atom in an excited state have a higher mass than when in its ground state? Does an atom in an excited state have a higher mass than when in its ground state?

Friction is commonly thought to arise from the electromagnetic forces of the atoms at the boundary between two surfaces in contact. However it occurs to me that, in addition to charge quanta, there are also mass quanta present in this system and they could very well play a role. Now, I'm just...

Suppose there is a 1 million solar mass black hole. A 1.022MeV photon near a nucleus produces an electron-positron pair a distance=A from the event horizon. The positron’s vector is directly “up” away from the singularity. It doesn’t have escape velocity. It reaches an apogee at distance=B from...

Problem Statement: How does the Higgs field “give mass” Relevant Equations: The exact way that particles interact with the Higgs field and therefore create mass. I’m trying to figure out how the Higgs field works, one problem is that while I originally though of the Higgs field like a medium...

Hi everyone, I understand that the phenomenon of running charge predicted by QFT has been experimentally verified: the physical charge on an electron really does vary with the energy at which it is measured. I have two questions: (1) Does anyone know what the canonical experiments confirming...

Hi all, I have a problem that I've been grappling with for the past 2 hours. I was confident at first that I found the correct solution, but when I tried to verify I didn't have a constant in my v(x) function. Here is my attempt: I appreciate your help kind internet strangers!

Problem Statement: A known mass at a know velocity collides on a spring of known stiffness. What is the equation that governs the deceleration of the mass, so that the force on the spring could be found? Relevant Equations: 1/2 m*V^2 = 1/2*k*x^2 + 1/2*m*(Vo)^2 Kinetic energy of mass before...

Hi. I have a question regarding the above image and want to know whether I am right or not. In the image there is a body with mass m and in the middle of the body there is a spring. The body is pulled upwards and then it hits two fixed rods such that the body cannot move upwards any more. Now...

In a recent thread we discussed the idea that an object slowly dropped into a black hole, can have its rest mass recovered, as energy, if slowly brought to a halt at the event horizon. Once the object is dropped, it would be unrecoverable, and the BH would gain no new mass. I am under the...

How can san object lose mass? You can use Antimatter or Fission or Fusion to turn it into energy. Also, one can just cut a piece of the object off. But are there any other ways to remove matter from an object? (Feasable and theoretical)

I thought I should use the ideal gas law to find out moles of air that would be transferred out through the window but the temperature and volume outside is not known. Can you help me further? thanks

My attempt: Proton 1.00728ux6+ Neutron 1.00866ux6=12.09564u 12.09564u-11.9967u=0.09894u E=mc^2 E=0.09894x(3.00x10^8ms-^1)^2

Hello. I'm a graduate student in electrical engineering, and I'm taking a class in semiconductor physics. My professor has used this equation for the energy of an electron in a semiconductor: $$E=\frac{\hbar^2 k^2}{2m^*}$$ This seems to imply that energy is inversely proportional to mass, i.e...

I was reading another thread which has been closed, so I cannot ask this question there. The question is about a post by @PeterDonis (post #21). https://www.physicsforums.com/threads/what-happens-to-the-inertia-of-a-mass-falling-into-a-black-hole.970627/ There are no internal pressures inside a...

Hello I have learned about conservation of momentum, Newton's law (1st, 2nd, 3rd law + free body diagram), conservation of energy and finding center of mass of several 2 D and 3 D shapes (non - calculus method). I watched youtube video about two objects connected by horizontal spring and in...

I don't understand what I am supposed to do. I know how to find the acceleration of the system, but I am not sure how to find the com acceleration. My guess would be something along the lines of xcom = (m1a1*x + m2a2*x)/(m1a1 +m2a2). Then do the same for the y axis. Then to find the velocity all...

The fig. 1.1(a) is a mass m attached to a spring that is fixed to a wall. I don't understand what does "a sudden momentum impulse" means. Is it an external force o what? I imagined that the new equation of motion would be md^2x/dt^2+dp1/dt-kx=0 md^2x/dt^2+mdv1/dt-kx=0 is this the equation i...

Hello I have no idea why underline part of my pic says like that. "Radio observations show that the component of this motion perpendicular to the Galactic plane is at most 0.4 ± 0.9 km s−1" So What? Why this sentence shows the mass?? ("The radio emitting source(underline part)" = Sgr...

A previous thread outlined the problem with a correct answer, however I don't understand where they got the formulas from. Here are the steps I've taken so far: 1. Convert 2*10^8 years to seconds = 6.3072*10^15 seconds (period,T) 2. The previous thread then went on to say you plug period and...

What are the steps to calculating the center of mass for this object? I don't want a numerical answer just the theory. I understand I need to calculate COM for all axis, we know in the Y axis it's dead centre because of symmetry but I don't know how to do it for the others. A hint would be...