Body Definition and 1000 Threads

I'm having the hardest time understanding Black bodies. I have a lot of questions about them so I can't write all of them, instead I'll just start with : Why are stars considered black bodies?

Why does a voltage tester (that looks like a screwdriver) turn on even when you are "heavily" insulated from the ground e.g. sitting on a wooden chair. Is it the result of capacitance between the human body and the ground? (i.e. the body and the ground act as conductors, whereas the insulated...

Hello I am wondering, does a black body release energy as heat, or does it only absorb all energy that basically comes into contact with it? Thanks

When a car turns there is a centripetal force acting at the tyres to get it round the bend. There is also an acceleration of the chassis away from the bend acting at the centre of gravity. These combine to create a torque which causes the chassis to roll about the roll centre. Is this correct...

Homework Statement Here is a question in my textbook. I saw the answer, but no explanation was there. A stone is thrown vertically upward with an initial velocity v_0. The distance traveled by it in time \frac{1.5v_0}{g} is ______________. Answer is \frac{5v_0^2}{8g}. Homework...

Hey guy, I would like to ask a few question about force and free body diagram. First question, I conduct a compressive experiment a few day back, using compression machine to test the strength of different materials e.g., Aluminium, PVC and Ceramic. However there is one thing that I don't...

Homework Statement Around vertical axis ##O## a body on picture below (see attachment) is being rotated with constant angular velocity ##\Omega ##. On the circle we have a body with mass ##m##, that can feels no friction. Find position of that body as function of ##\phi ## and time. Calculate...

Hi Let's consider the three body problem. The motion of all bodies is a manifold of dim 18. But I will consider that the mass of the third body is neglictible and I am interested in the motion of the third body (in the case, this is the restricted three body problem (non necessary planar nor...

Homework Statement Consider a cuboid of lengths a, b and c along the x, y and z axes respectively, centred at the origin. The task is to show that the moment of inertia of the cuboid of mass M and mass density ρ about an axis along the body diagonal, from (-a/2, -b/2, -c/2) to (a/2...

Homework Statement This is not a HW problem, but something I am trying to prove/disprove for my own knowledge. I have a tube pinned at both ends and inclined in the x-y plane. The pin locations can both move freely in space but subject to the constraint that the tube will not stretch or...

For my senior physics research project I've developed an orbital analysis program that calculates the minimum \Delta V required (applied in an instantaneous impulse) to deflect an inbound Earth impacting asteroid. I've generated data for several different hypothetical orbits and now my advisor...

I am currently working on a robotic manipulation problem and need to form a model for how an object responds. I start by writing up the equations of motion for the body, the motion is then constrained by an additional constraint equation. However, I am new to the notions of twists and wrenches...

A ridig sphere is rolling from left to right down an incline plane with an angle elevation of β In the y -direction, FN = mg cos β. In the x-direction, mg sin β - f (where f is the frictional force: μsFN) The laminar motion is then given by Icmdω/dt = Rf (where R is the radius of the sphere)...

Homework Statement http://postimg.org/image/vnn9m9au9/ For the car why is the friction acting towards the left. Shouldn't it be towards the right since the car is moving to the left And why is there no friction for the trailer? Homework Equations The Attempt at a Solution

Momentum of a body can be constant while it accelerates? I mean if velocity increases while mass decreases proportional. And if is true, what force produces acceleration?

Hello there! I am currently studying the equilibrium of rigid body and encountering a doubt. Now, in their explanation of reaction forces by a roller or a rocker or a smooth surface, they generalize it as in the preceding examples prevent the translation of a beam for example in ONE direction...

Homework Statement Find the unknown mass on a lever (see-saw). I have three masses. To the right of the fulcrum, the mass is 166 g and it is 25.15 cm from the fulcrum. There are two masses to the left. One is 166 g and is 16.95 cm from the fulcrum. The unknown mass is 3.33 cm from the fulcrum...

What is the lower mass limit for a body to have rings? I'm thinking that Chariklo, at 155 miles in diameter is pretty small. Gravity would be so weak you'd have to hold on just to not 'jump' off with every step. Cheers, 3point14rat

What temperature would the human body need to be in order to sustain all necessary metabolism reactions in the absence of a catalyst? I know this is unreal, I am just curious of an order of magnitude estimate.

Hi, Consider a body is traveling with a velocity in a direction for infinite time. If anything does not disturb that body. It will come to its initial position for a time ?

A 60kg student is standing on a scale in an elevator that measures weight in Newtons. Calculate the reading on the scale if the elevator is accelerating down at 4 m/s^2...when the elevator is accelerating up at 4 m/s^2... and in free fall. Not sure if my work/answer is correct accelerating...

Hello, my question id the following: when using Tsiolkovsky's equations to determine the velocity of a body after certain period of time, when the engine of a (space)craft is running, life is simple. But how do you calculate the falling rate of an object that is constantly falling, and then...

I was watching a video by ASAP science in which they said that the body is capable of telling time. We don't need alarm clocks, we can wake up on our own, due to some fluids in our body. How exactly does this work?

So we're studying resonance. It says that it occurs when an external periodic force acting on a body is exactly equal to the natural frequency of the body. The body then begins to vibrate with greater/increasing amplitude and intensity. And so what I want to know is that is there a...

Homework Statement http://postimg.org/image/5h0hvdi4l/ Can someone explain why the FBD of Block C would involve three cord tensions? Homework Equations The Attempt at a Solution

Homework Statement Attached, where AC=BC=2R and CD=CE=3R. I need to work out the force the cylinder exerts on the cross section (in order to work out the moment at C). So first I'm trying to work out the free body diagrams for this system. Is it as I've attached? How do I draw the tension...

Hello Forum, Let's consider a particle that is giving an initial speed in a certain direction. The particle is now moving in that initial direction at a constant speed. If a later moment a force starts acting on the particle and the force direction is not along the original particle...

Hello, I would like to understand what exactly is meant by "calories" when we read for example that a chocolate bar has 300 kcal. I understand what is a (kilo)calorie. What I do not know is whether the written values are the raw values in calories or if they are the values our body can...

Hello, Do living beings use food to decrease the entropy of his body? If so, could anyone explain the process of how we do it? (or at least name a couple of keywords that I can search) Thank you very much.

Homework Statement So, we can presumably write that m = g L, where L is the angular momentum, g the ratio wanted, and m magnetic dipole moment of an axially symmetric body. Total mass is M, total charge Q, mass density \rho_m(r)=\frac{M}{Q}\rho_e(r), where \rho_e(r) is charge density...

I have been looking for information about the way Radiotherapy works and, needless to say, there is much more involved than just local frying of tissue. I have been told and also read, that the dose received in tissue is not necessarily maximum at the surface. For instance, the dose seems to be...

In other words, are there any circumstances in which one object, captured by the gravity of another, would simply trail behind it indefinitely, instead of revolving around it or crashing into it? Is it possible? It seems reasonable to me that under certain circumstances it could happen, but...

1. 6. A 100 W light bulb is designed to operate with it’s filament at 2000K. If the filament is a perfect cylindrical Black Body and 2 cm long, i) What must it’s diameter be (3 marks) ii) What will be the wavelength of the intensity peak in its emission. (2 marks) iii) You...

Hello All, I've been searching for days to try and solve this but I'm going round in circles so thought I'd fire it out to into the ether! I'm analysing a gantry system that is essentially cantilevered from one end but the part of the problem I'm struggling with can be simplified thus...

Car--Hill--Free body A car coasts at a constant speed over a circular hill. Which of the free-body diagrams in the figure attached is correct? Explain. My attempt: I am thinking B. Since the car is at a constant speed, there's no acceleration. So there is no additional force acting...

Homework Statement A cylinder of length 0.02m emits 100W and is at 2000K. It is a perfect black body. What is it's diameter? Homework Equations Planck's Law: B(λ,T) = http://en.wikipedia.org/wiki/Planck's_law solid radian = A/r^2 (not sure if needed or not) The Attempt...

The velocity of any point P of a rigid body in rotation plus translation is \vec{}vp=\vec{}vCOM+\vec{}vp,COM. Now |\vec{}vCOM|=v and \vec{}vp,COM =rω . But v and rω are same thing as v=rω ,so velocity of the particle every time will be √2 v.Then what is the difference between \vec{}vCOM and...

http://www.aapt.org/physicsteam/2012/upload/exam1-2011-1-3-answers_1.pdf Homework Statement You are given a large collection of identical heavy balls and lightweight rods. When two balls are placed at the ends of one rod and interact through their mutual gravitational attraction (as is...

Problem goes like this.. body falls toward a planet with acceleration of -g0*R^2/s^2. where R is the radius of planet 4000 miles, g0 is 30 ft/s^2, s is the distance of the body from the planets center. the initial distance of the body from the surface is 400 miles. find the impact velocity...

Homework Statement Draw a free body diagram of the incline. Build the free body diagram of the man. Which is the force which makes the man to go up the incline? http://imagizer.imageshack.us/v2/800x600q90/46/t92m.png Homework Equations Newton's 2º Law The Attempt at a Solution...

Hi! I'm a science fiction writer and need to know if a body would decay in a microbe-free environment. I have a killer running loose on a space station (far future). He kills and leaves a body in a secluded area. After a couple months, would the body have decayed? To what extent? Thanks for the...

refer to the following image so consider the angle of the yellow theta on the top left. this is 45*. if we fix one side of both red lines at the blue circles, and we slide the other end along the green side of the cube, ie just think of the green lines as rails for the red lines to slide...

Hello, I'm trying to prove a simulation of mine is working correctly. the simulation has a cube of sides 1, mass 1 and c.o.m. position at (0,0,0.5) ie sitting on the xy plane. i have a force along the x-axis of 10. Is there anyway given those two, that i can work out the resulting ω and v of...

Dear All, i was reading a book in which it is written that if a rigid body have both rotational(with angular velocity 'w' about its center of mass)and translation(with velocity 'v' of center of mass) motion then the whole motion can be treated as an equivalent motion of pure rotation about...

Homework Statement In the diagram attached a bar weighs 500 kg and is a 2D plane rigid body with mass centre at G. At the instant shown, the bar is moving horizontally at but reducing speed, causing horizontal deceleration as shown by vector a=-7i m/s2. At the same time, the bar is being...

Homework Statement The given force F is equal to 5000N,γ=〖30〗^o and α=〖15〗^o. The moment on member 4 is to be found. The geometry of the structure was worked out separately. Homework Equations To solve the problem I tried to use the Equilibrium equations which state that...

Homework Statement https://www.icloud.com/photostream/#AE5oqs3qHTNWQ;B21C49F3-02FB-4EA3-8CE5-D1E2C1FA7C49 Homework Equations The Attempt at a Solution https://www.icloud.com/photostream/#AE5oqs3qHTNWQ;A55D9431-FD6D-4884-9AFC-C4D7C8E39AF1

Greetings folks, I'm new to this forum and to physics in general so apologies if I come off like a greenhorn or if I am posting these questions in the wrong place. I have an Arts background and have never really "gotten" science, but my interest in post-Enlightenment philosophy has led me to a...

My current level of knowledge is based on Physics I and my own readings, so bear with me if this is something relatively simple that I'm overlooking... Anyway, my question is regarding the energy required for an orbiting body to escape orbit? I understand the formula of escape velocity where...

Hello, I don't think I really understand the derivation of an equation of motion for a falling body under the force of Earth's gravity... I'm a little ashamed by this. I haven't been able to find someone asking quite the same question as I am about to ask. I completely understand that the...