Zero Definition and 1000 Threads

You may think you've seen this before, since I've seen similar discussions in the archives of this, but I think I've distilled the thoughts down to a couple of facts that contradict the common beliefs regarding relativity. Let me preface this with a basic observation: Lorenz invariance does not...

I learned this in college too. I once know the name of these zero friction piston rings but I have forgot. If I knew the name I could do Google search and learn more about them. College professor said, grooves are .020" wide and .020" deep. Pressure drop across the grooves make them act like...

Homework Statement Is the work zero here because its a frictionless surface? If, so why? If not then what's the reason and why? Homework EquationsThe Attempt at a Solution I was originally thinking 1/2mv^2 .. but KE is zero right, but having it be mgh didn't make sense..

Hi. Is infinity multiplied by zero defined and is it zero ? And is infinity multiplied by any positive number , infinity ?

1. The problem statement Two charges of 3μC and -2μC are placed 2cm apart. At what point along their connecting line is electric potential zero? Homework Equations Electric potential superposition Φ=Φ1-Φ2 since q2 is negative Φ=kq/r^2 The Attempt at a Solution Let’s say the charges are on the...

Is the weight of a small satellite in its orbit zero?

Hi, I have decided I like to learn some physics as I know absolutely zero physics and also including chemistry or biology, and I’d like to learn a bit of all 3, to the high school level perhaps. It seems that from, what I’ve read if I want to learn chemistry, I’ll first have to know physics, and...

Zero gravity. We can hear about the zero gravity chamber , zero-g flights on aeroplane and lots of other stuffs about zero gravity on earth. How does it actually works? Can it be possible for us to make it?

Hi guys! Here's a problem i was working on. I solved it by root test and got absolute value of x on the outside of the limit and the limit equaled zero. Is it wrong to multiply the outside absolute value by the zero I got from the limit? or is that okay? In general, when we are solving power...

Find the zeros $$f(x)=16x^4+3x^2-2$$ ok I presume we can solve this with the quadratic formula even with powers of 4 and 2 by setting $u=x^2$ I was able to get$$x=\pm\sqrt{-\frac{3}{2}+\frac{\sqrt{137}}{2}}$$but $W\vert A$ says the answer...

Hello. I have a question about how close (in time) the Hot Big Bang theories formulated before 1980 could be reliably extrapolated to T zero. In his book... https://en.wikipedia.org/wiki/The_Inflationary_Universe ...Alan Guth recounts a lecture by Robert Dicke in 1978 which set the benchmark...

Description of the Problem: Consider a spring-mass system with spring constant ##k## and mass ##m##. Suppose I apply a force ##F_0 \cos(\omega t)## on the mass, but the frequency ##\omega## is very small, so small that it takes the system, say, a million years to reach a maximum and to go to 0...

Homework Statement A block of mass 2.42kg is accelerated across a rough surface by a rope passing over a pulley, as shown in the figure below. The tension in the rope is 13.9N, and the pulley is 12.3cm above the top of the block. The coefficient of kinetic friction is 0.395. A: 2.28 m/s^2...

What do people think of Fulvio Melia's argument for the necessity of "zero active mass" in FRW cosmologies? (i.e. the overall equation of state must be ##\rho+3p=0## at all times) Here is a link to an interesting lecture video: Here is a recent paper: https://arxiv.org/abs/1807.07587

Homework Statement If a = 9-v² then prove that v = 3 (e^6t - 1)/(e^6t + 1) the condition when t=0 also v has zero value Homework Equations I don't quite understand in this but general equation should be dv/dt = a The Attempt at a Solution Actually i don't don't have any idea in this problem...

Hi. x2 = x3 / x but x2 is defined for all x and equals zero at x=0 but what happens for x3 / x at x=o ? Is it defined at x=o ? Does it equal zero ? If not what is causing this anomaly ? Thanks

I start by outlining the little I know about the basics of quantum field theory. The simplest relativistic field theory is described by the Klein-Gordon equation of motion for a scalar field ##\large \phi(\vec{x},t)##: $$\large \frac{\partial^2\phi}{\partial t^2}-\nabla^2\phi+m^2\phi=0.$$ We...

Does ideal fluid have zero surface tension? What does zero surface tension signify?

Here's the scenario: If a force is accelerating an object at a constant rate, and force is removed, does the acceleration instantaneously go to zero? The problem i see with that is that on the graph, the acceleration line would be constant, horizontal, and then when the force is removed to...

Homework Statement There are 2 situations- 1)a rod of length L is lying on a smooth horizontal surface with its one end hinged to the ground, a ball traveling with a velocity v hits its other end and comes to rest, How is the net external torque about hinge point O zero? 2) in the second case...

Hi all, I have performed a small static analysis with one element (C3D8). The bottom face of element is completely constrained, and the top part is displaced. In the geometrical linear analysis, the internal energy (ALLIE) and the work done (ALLWK) are equal. So, with ETOTAL = ALLIE - ALLWK...

I am interested in the following theorem: Every field of zero characteristics has a prime subfield isomorphic to ℚ. I am following the usual proof, where we identify every p∈ℚ as a/b , a∈ℤ,beℕ, and define h:ℚ→P as h(a/b)=(a*1)(b*1)-1 (where a*1=1+1+1... a times) I have worked out the...

Let (A,+) be an Abelian group. Consider the ring E=End(A,A) of endomorphisms on the set A, with binary operations +, and *, where (f+g)(x)=f(x) + g(x), and (f*g)=f∘g. I have tried to find zero divisors in this ring, but I just couldn't come up with an example.

Let f:\mathbb{R}^m\rightarrow\mathbb{R}^m. Define the zero set by \mathcal{Z}\triangleq\{x\in\mathbb{R}^m | f(x)=\mathbf{0}\} and an \epsilon-approximation of this set by \mathcal{Z}_\epsilon\triangleq\{x\in\mathbb{R}^m|~||f(x)||\leq\epsilon\} for some \epsilon>0. Clearly \mathcal{Z}\subseteq...

I am trying to compare an experiment on spinal changes due to zero-g in astronauts. Researchers simulated zero-g spinal elongation by suspending human subjects so that no part of their body touched the ground. This figure shows the % change in disc thickness for each subject compared to data...

Hi. I'm trying to get an idea how to look at the beginning, before the cosmic background radiation (CBR) and what we can detect with our eyes, and what we can assume about earlier times than light was around. I was looking into the red shift effect effect, as not only a measure of relative...

Homework Statement Hello, I have a problem I don't want how to approach, it is a little weird. It is a problem of equilibrium (torque) The situation and my approach is in the picture I uploaded. A beam is supported by the blue structure. On the beam it is a person(100N) at a distance of 3m in...

The other day I was pondering what happens at/near absolute zero so I did some googling and found articles talking about how it has been demonstrate that as you near absolute zero, the quantum effect start to have an increased range. However, is seems that perhaps the quantum effects only get...

What is effective mass? What is zero and infinite effective mass?

Homework Statement If I have two eigenfunctions of some operator, that are linearly indepdendent e.g ##F(x) , G(x)+16F(x) ## and ##F(x)## has eigenvalue ##0##, does this mean that ## G(x) ## must itself be an eigenfunction? I thought for sure yes, but the way I particular question I just...

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...

In the following wiki article for Beltrami flows, it is stated that the nonlinear terms are identically zero. I can easily prove the terms are equivalent and thus cancel one another, to yield the linear equation. But after a bit of algebra, I don't see why the terms are zero themselves? Why...

Having seen plenty of 'vacuum in a tube' tests on youtube I am wondering how a human can work in such an environment. I'm trying to understand how a space suit can be tested before it is used 'live' in space, and how seemingly 'everyday' materials are used to protect astronauts from the harsh...

Homework Statement 11.7 The motion of a particle is defined by the relation ##x = 2t^3 - 15t^2 + 24t + 4 where x is expressedin meters and t in seconds. Determine (a) when the velocity zero , (b) the position and the total distance traveled when the acceleration is zero Homework EquationsThe...

Homework Statement Charges q1= +3 nC and q2=+8 nC have a separation distance of d= 12 cm. Find the point where the electric field is zero. Homework Equations E=kq/r2 The Attempt at a Solution I approached this problem as follows: 1) I assume the point where it happens is between charges, on...

In the nuclear physics, why do we say that the total angular momentum J is zero when the proton number Z and the neutron number N are both even?

In the book 'ZERO THE BIOGRAPHY OF A DANGEROUS IDEA' Charles Seife says, "Because ratios were the key to understanding nature, the Pythagoreans and later Greek Mathematicians spent much of their energy investigating their properties. Eventually, they categorized proportions into 10 different...

In my introduction to quantum mechanics, I learned about the particle in a box, followed by the quantum harmonic oscillator. In both instances, zero energy was not possible; the ground states had non-zero energy. However, in deriving the solutions to the Schrödinger equation for a particle on a...

1.Problem statement Prove the average external force of a system of particles N starting from rest and ending at rest is zero.Homework Equations If the system moves periodically prove the av. external force is zero in a period The Attempt at a Solution I don't quite understand what i am asked...

1. Problem Statement An astronaut is playing with a ping pong paddle and ball in zero gravity. The astronaut is 12m from a flat wall and floating toward it at 4m/s . A ping pong ball bounces back and forth between his paddle and the wall at 11m/s. Eventually, the astronaut reaches the wall and...

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...

Homework Statement :[/B] limx->0xsin(1/x)Homework Equations : [/B]-The Attempt at a Solution :[/B] I feel the limit does not exist. Because sin(1/x) is largely changing value as x approaches 0,(since it is an oscillating function), and in limit, we check what happens in neighborhood of the point...

Homework Statement So I have these two Matrices: M = \begin{pmatrix} a & -a-b \\ 0 & a \\ \end{pmatrix} and N = \begin{pmatrix} c & 0 \\ d & -c \\ \end{pmatrix} Where a,b,c,d ∈ ℝ Find a base for M, N, M +N and M ∩ N. Homework Equations I know the 8 axioms about the vector spaces. The...

If one considers the quantized levels of E, for the solutions to the Schrödinger eqn,, then I am wondering: what are the lowest possible energies that can occur for the Schrödinger eqn? I take the highest possible energy is at the classical limit, but is the zero-point energy the absolute...

According to [Dark Energy and the Accelerating Universe](https://ned.ipac.caltech.edu/level5/March08/Frieman/Frieman5.html) quantum field theory says that the energy density of the vacuum, ##\rho_{vac}##, should be given by $$\rho_{vac}=\frac{1}{2}\sum_{\rm...

Homework Statement [/B] A block travels in the positive x-direction with some velocity ##v_0##. It is subject to a drag force $$F(v)=-F_0e^{Kv},$$ where ##F_0,\,K## are positive constants. Find the point in time when the velocity of the block momentarily goes to zero. Find how far the block has...

Hi, I was wondering what is the physical meaning of these integrals: \begin{equation} \int_{-\infty}^{\infty} \psi \psi^* dx = 0 \end{equation}\begin{equation} \int_{-\infty}^{\infty} \psi x \psi^* dx = 0 \end{equation} \begin{equation} \int_{-\infty}^{\infty} \psi p \psi^* dx = NA...

Hi, did the energy of the universe, right before big bang equal to zero? And if so, does zero as zero-point energy in relativistic theory and quantum mechanics make any sense? If this is not possible, are there any models, including the standard model, SUSY or QFT which consider ground state...

Hi, is there an alternative form of the zero point energy for free electrons, where there is no space interval L to be quantized in? The zero point energy for electrons in an atom can be simplified to a variant where Z^2 is present in the nominator, however, these are not free electrons. Can a...

I'm currently studying Thermodynamic properties of a Fermi gas at the absolute zero temperature. I get how the internal energy, pressure... etc of the gas are derived. For example, in computing the internal energy, one sums up all the energy of states weighted by its average occupation...