Body Definition and 1000 Threads

Does the nature of radiation emitted by dense bodies like black holes differ in frequency from radiation emitted by regular stars like our Sun ? I believe that the former radiates more x-rays and high frequencies rather than the latter which radiates mainly uv, visible and infrared ranges. Is...

Homework Statement Two equal isolated metallic bodies A & B start with no charge and zero potential. A is given a charge giving B the potential U. B is then Grounded giving A the potential U. What potential did A have before B was grounded? Hint: Use symmetry and use potential coefficients...

Homework Statement I don't understand, physically speaking, how do we get from the first equation to the second: how do we get the fact that velocity in body fixed frame equals to angular velocity in body fixed frame. Furthermore I dont' understand how we get the angular velocity in inertial...

Homework Statement Attached is a pdf of the assignment problems, I'm looking at problem 1 under the "Try" section. It shows a rod attached to a wall bracket on the left, with a force applied on the right side. I'm also including a link to the solution, it's under "Problem 3.83" -...

I am new to elastic theory. I have a question about elasticity. We assume we have a body with no internal forces. Surface forces are applied on the border. Can we leave the elastic domain (reach the yield surface) in an interior point without leaving the elastic domain on the boundary? If no...

Hi. Let's say we have a black hole of limited mass, say a few solar masses, and it encounters a much more massive object which is not collapsed into a black hole, say a very massive star, in principle it seems that some giant stars have been detected with masses over 100 solar masses. So let's...

Dear all, I needed help in finding a source where the derivation of radiation emitted by a dielectric body is laid out. The derivation of spectral density of radiation emitted from a blackbody at a temperature ##T## is given in many books by populating the energy states using Bose-Einstein...

A body in an absolute vacuum is suspended from an axle having no friction at the body or at the suspension points. A power source is affixed to the body which rotates the axle. At rest the body is horizontal. The body weighs 4000 lbs. The center of gravity of the body is vertically 4 ft. below...

Hello, It looks like Stefan Boltzmann Law can be used for a lot of different purposes: to calculate the temperature of stars, sun, temperature of the Earth's sky, temperature of particular surface, wall, the radiation emitted by the body by knowing its temperature, and so on. What confuses me...

Referring to slides 3-4 (page 2) of this link: https://www.princeton.edu/~stengel/MAE331Lecture9.pdf The author states the relationship between body rates [p q r] and Euler angle rates [φ_dot θ_dot ψ_dot]. I want to verify this but have been failing miserably... My reasoning: 1) p, q, and r...

Hi, I am trying to build (or at least conceptually) design a diy autonomous lawnmower. I want to add an automated grass cutting height mechanism. I have never worked with lawnmowers but through basic googling know that most lawnmowers have simple mechanisms in wheels to change cutting height...

Ok so what I want to create is a simulation of how the acceleration of a person falling would change according to the person's mass and height. This would then be explored in Matlab. Therefore, first, I am trying to find out the equations that would relate acceleration motion with mass and...

I know to describe Quantum Mechanical systems we can use: -Schrodinger equation -Feynman Path Integral method -Heisenberg Matrix formulation Well my question is, if you want to calculate molecular properties, and want to understand biochemistry (protein), you have a system with several...

Consider a piece of pure Fe hot enough to have a bright white color (about 2 000 ºC, e.g.) and the characteristic yellow narrow yellow emission of the Na atom. Does the Na yellow band will be present at the thermal spectra of the pure Fe? My guess: Yes.

First of all, Thank you very much for you time if you're reading my question. I just want to know how things work (i guess all of us), and some guidance will be more than welcomed. One of the questions that i have in my mind is: Could the sound waves (e.g:a song or a sound) make some...

So, basically... Since I have my own place/office, tools, machines and everything I need. I've been working on a steel suit just for fun, as a hobby. Based on the Iron Man superhero, and I want it as my Halloween costume this year. My idea is to build it gorgeous, and I'm on that at the moment...

Consider the path of a proton at 7 TeV Ke at LHC. Wikipedia says: Length contraction is the phenomenon of a decrease in length of an object as measured by an observer which is traveling at any non-zero velocity relative to the object. This contraction (more formally called Lorentz contraction...

Homework Statement A 75-kg man pushes a crate 4.5 m up along a ramp that makes an angle of 17.5° with the horizontal. He exerts a force of 510 N on the crate parallel to the ramp and moves it at a constant speed. Calculate the work done by man to move the crate, in joules. Be sure to include...

In the above cases I want to find the acceleration a for m1. I can do it by considering m1 and m2 to be a system, which would give me a = F/(m1+m2). How can I use a free-body diagram instead to calculate the acceleration? Using a free-body diagram, m2 only affects the vertical motion by exerting...

Hello everyone! I'm new to this site, and I'm looking for some help regarding a short story that I'm writing, specifically about the condition of bones (and the remains of a brain) that have been buried for about 5-7 months. I've seen a similar thread, but it didn't really answer my questions...

Homework Statement Suppose you walk into a sauna that has an ambient temperature of 57.0°C. Calculate the rate of heat transfer to you by radiation given your skin temperature is 37.0°C, the emissivity of skin is 0.95, and the surface area of your body is 1.60 m2. I solved this first part and...

According to my textbook, in the derivation for the effective potential U_{eff}, starting with the Lagrangian L = \frac{1}{2}\mu(\dot r^2 +r^2\dot\phi^2) -V(r), substituting into Lagrange's equation gives \mu\ddot r = -\frac{\partial V}{\partial r} + \frac{l^2}{\mu r^3} =...

I understand that this will vary from human to human, but how much weight is exerted, in total, on the average adult human body. It would be very much appreciated if the calculations can be shown. Thanks!

Homework Statement A rigid body is made of three identical thin rods, each with length L = 0.530 m, fastened together in the form of a letter H, as suggested by the figure here. The body is free to rotate about a horizontal axis that runs along the length of one of the legs of the H. The body...

in rigid body dynamics is this relation between velocity of centre of mas and velocity of any particle in the rigid body correct? vcm = vp + rXω r is the position vector of the particle with respect to centre of mass relations are written in vector form and also tell me how to calculate...

Homework Statement A disc of mass M and radius r is kept on a horizontal,frictional plane and is connected to a horizontal spring at the centre.A particle of mass m strikes the topmost point of the disc,tangentially and sticks to it.Assume that the mass of the particle is m and it's velocity is...

Hi Friends, I am trying to find variation in capacitance between two plates with applied body load. I defined an air box around the plates. Now I'm trying with electromechanics physics for applying body load and finding capacitance. I defined the two plates as linear elastic material. Applied...

From the last few sentences of the below attached paragraph, when the inertia ellipsoid is prolate, the body cone rolls outside the space cone; when it is oblate, the body cone rolls inside the space cone. Whether the body cone rolls outside or inside the space cone should depend on whether the...

For the rotation of a rigid body about a fixed axis z the following holds. $$\vec{\tau_z}=\frac{d\vec{L_z}}{dt}= I_z \vec{\alpha} \tag{1}$$ Where \vec{\tau_z} is the component parallel to the axis z of a torque \vec{\tau} exerted in the body; \vec{L_z} is the component parallel to the rotation...

I'm studing Gauss law for gravitational field flux for a mass that has spherical symmetry. Maybe it is an obvious question but what are exactly the propreties of a spherical simmetric body? Firstly does this imply that the body in question must be a sphere? Secondly is it correct to...

http://phys.org/news/2016-04-metal-foam-obliterates-bullets.html The CMF armor on collision literally converts the projectile into small particles, spraying out. This is interesting and definitely not my area. Watch the attached video. Questions: 1. the particles resulting from the hit have...

Why is ##a_{ji}dG_j'=dG_i'## ? from the third last line below. ##G_i=a_{ji}G_j'## because a vector labelled by the space axes is related to the same vector labelled by the body axes via a rotation transformation. If ##a_{ji}dG_j'=dG_i'##, then we are saying a vector ##dG'## labelled by the...

Ham goes bad if you leave it there for a few days but why doesn't human body goes bad if you leave it there for a few days and when the person is alive?

I 'd like to clarify some doubts about the rotational motion around a fixed axis of a rigid body, in the case the angular momentum vector \vec {L} is not parallel to the angular velocity \vec {\omega} . In particular, consider a horizontal barbell with two equal masses m , forced to rotate...

Why is Planck radiation the greatest amount of radiation that anybody at thermal equilibrium can emit from its surface, whatever its chemical composition or surface structure?

Homework Statement Homework Equations relevant equations are provided with each question below The Attempt at a Solution please check my solutions to ensure they are correct. thanks. a) [/B] b) Calculate net force: Fnet = FA + Ff + Fg Fnet = (1.20 x 104 N [up]) + (1.40 x 103 N [down])...

I've been hearing of many athletes coming forward to donate their brains to science when they die. Curious with most of us being involved in science and its progress has anyone here made plans to donate their body or an organ to science after they die? Why not? Let's do it!

Homework Statement A spherical body of area A and emissivity 0.6 is kept inside a perfectly black body. Total heat radiated by the body at temperature T is (A) 0.4σAT4 (B) 0.8σAT4 (C) 0.6σAT4 (D) 1.0σAT4 Homework Equations Stefan-Boltzmann's Law: P = AεσT4The Attempt at a Solution If it wasn't...

Homework Statement A metal rod of length ‘L’ and mass ‘m’ is pivoted at one end. A thin disc of mass ‘M’ and radius ‘R’ (<L) is attached at its centre to the free end of the rod. Consider two ways the disc is attached: (case A) The disc is not free to rotate about its centre and (case B) the...

Hello Forum, A black body is an object with emissivity=1 that absorbs as well as it emits. Does that mean that its temperature T stops rising after it reaches thermal equilibrium but it rises before then since absorption dominates over emission? What about a white body? That would be a perfect...

Asked in 2015 on "Quora," a PhD candidate answered that near-infared wavelengths can penetrate the body more that visible wavelengths, but only by a millimeter or two. She sums up her answer, "So the question: can NIR light penetrate the human body? The first millimeter, yes, through the chest...

When we looked at some closed surface, we defined the overall electric flux of that surface as the sum of all infinitesimal fluxes of all the infinitesimal surfaces that make the quoted closed surface. Does that change if we do not have a closed surface, but a rigid body such as, let's say, a...

Homework Statement for part b , why when t = 0 , x= 0 , why not x =100 ? the author gave that the object drop from height of 100ft at the start of the question. Homework EquationsThe Attempt at a Solution

all of automate system in our body. digesting food, put oxygen on our blood and pull carbon dioxide out, immune system, wound healing...etc does our brain control all that even without our awareness? or those can still work even without brain order?if true... wow, our brain may inferior to...

Homework Statement In a dark room with ambient temperature T0, a black body is kept at a temperature T. Keeping the temperature of the black body constant (at T), sunrays are allowed to fall on the black body through a hole in the roof of the dark room. Assuming that there is no change in the...

I'm not sure this is the best fourm to post this, but... How much heat, preferably in watts, does perspiration dissipate under mild exertion (i.e. walking) on a 90° F day? Assume the individual is hydrated and not starving. Also assume they weigh 180Lbs. How much heat would have to be...

Hi! I am trying to simulate the rotation of a planet around a star, using the 2nd order Runge-Kutta method (I am starting with this and I will try 4th order later, I am new to this topic). I have this code but it doesn't work. When I plot y(x) I should get a circle, but I don't get it. Any idea...

Homework Statement The context of this problem involves a dolly pulling a trailer, and I am trying to establish the basic free body diagram for the trailer. Is what is done so far acceptable and is this a step in the right direction? Homework EquationsThe Attempt at a Solution I am confident...

Homework Statement Hi everyone. I'm a high school teacher. My background is physics and math, but right now I'm teaching a course that involves some basic (grade 10) biology. I don't know much about bio, so I need your help! Right now, we're studying the organelles. I'm trying to put together...

suppose a platform "P" is rotating about the z-axis wrt x-axis . another platform "Q" rotating about z-axis below "P" with same angular velocity wrt x-axis standing on Q , P is at rest wrt Q, After some time rotational inertia of P about z-axis starts changing with time standing on Q , P will...