bodies Definition and 523 Threads

I finally found a result I believe for the the asymptotic metric (valid for large r) of a pair of bodies in a circular orbit emitting gravitational waves. I use spherical coordinates, ##[t, r, \theta, \phi]##. If we let the linearized metric ##g_{\mu\nu}## be equal to the sum of a flat metric...

Hi Guys While studying physics for my masters (doing it in material science engineering), huge amount of questions appeared. First, let's imagine two experiments 1) One enclosure with perfect reflective walls (R=1 over the entire thermal radiation spectra) at a temperature T1 and a body inside...

1. The problem statement: Consider a solid sphere and a hollow sphere, of equal mass M and equal radius R ,at rest on top of an incline . If there is no slipping which will reach the bottom faster. 2. Homework Equations : acm = Fext/M (cm= centre of mass) angular acceleration= torqueext/ I ( I...

I'm looking for the linearized metric in the far field for a pair of mutual orbiting bodies that are emitting gravitational waves (GW's). I gather finding this (approximate) metric should be possible using the quadrupole moment of the source. From Landau & LIfshitz "Classical theory of...

Homework Statement Homework EquationsThe Attempt at a Solution When the barrel starts to tip, the normal at point A should be 0 Newtons, and then all weight would be on point B. I'm guessing if the barrel would tip, it wouldn't be sliding across the floor so kinetic friction is not used...

A plane makes a trip of 246 miles. For some amount of time the planes speed is 115 mph. For the remainder of the trip the planes speed is 250 mph. If the total trip time is 72 minutes, how many minutes did the plane fly at 115 mph?

I'd like to get a general and clear picture of all the ways heat can be stored in a body. Suppose we have a kiln/furnace in which we put : particles a) electrons,... monoatomic molecules b) atoms of He... diatomic molecules c) atoms of H, O ... pieces of metal d) Fe, Cu... compounf...

Guys...Can anyone explain me why fluid accelerates and then decelerates when flowing over a convex surface and also concept of flow attachment in simple terms

Homework Statement A block and spool are each pulled by a string across a frictionless surface. The string is wound around the spool such that it may unwind as it is pulled, the string attached to the block is at the center of mass. The block and spool have the same mass and the strings...

Hello everyone. I am doing an studi on Be stars, all of which are inside the Milky Way, I want to show that the red shift won't be a big deal here, but I am confused about how to prove it; what I have done is combining the equations λr=λe(1+z) and cz=Hd to get λr=λe(1+Hd/c) where z=v/c. I get...

I saw this problem in my dynamics class: http://d2vlcm61l7u1fs.cloudfront.net/media%2Fa22%2Fa2261e7a-0e85-45e7-8b63-f23157d623bc%2Fphp37ql1a.png I know how to solve it, but I don't understand why A(bd) has both a normal and tangential component to acceleration. If it is rotating at a constant...

Hi there, I was reading up on how planets are classified based on their size, but ran into a problem when I began to consider rogue celestial bodies. If a body has significant enough mass to maintain a hydrostatic equilibrium, yet doesn't orbit a star, I understand that it's classified as a...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Here is something that some one asked me, as their homework question, and it stumped me. A star is seen orbiting a black hole. The black hole's mass is 6.0E30 kg (approx, 3 solar masses). The...

Hello, I'm a student in Higher School Preparatory Classes, I'm doing a research on "the dynamics of celestial bodies". I already included some notions of the motion of planets around the sun and the solar system around the center of the galaxy in my research, but it is not enough. I need...

I was told in my cosmology class that there are two planets separated by a distance L at time t = 0. L is known as the co-moving distance between the planets. I was told the equation for proper distance, ##d_p##, is given by: ## d_p = a(t) L ## where ##a(t)## is the spatial expansion factor of...

Hi. The formulae for the velocities of two bodies after a perfectly elastic or inelastic bodies, let's say in 2D, (e.g. billiard) can be derived from three equations: conservation of energy and conservation of momentum in two dimensions. But how do you treat collisions of three or more bodies...

I understand earthing as - if we Earth a charged body, its charge distribution changes such that, its potential becomes zero. So now I have a doubt that if we have 2 charged spheres(Q1 , Q2) ,separated by some distance and then if we Earth one of them , then how will the charge distribution...

I am in introductory physics, and have just been introduced to the topic of toque. For forces in translational motion, I know that we idealize objects to be point particles. However, when it comes to torque, we don't deal with point particles, but with "lever arms." I guess essentially my...

Homework Statement A solid sphere is rolling without slipping on rough ground with an angular velocity w and linear velocity v. It collides elastically with an another identical sphere at rest. Radius of each sphere is R and mass m. What is the linear velocity of the first sphere after it...

Homework Statement 1. It has been argued that power plants should make use of off-peak hours (such as late at night) to generate mechanical energy and store it until it is needed during peak load times, such as the middle of the day. One suggestion has been to store the energy in large...

Homework Statement i want to know about the variation in pressure according to varo=ious depth in different water bodies like for river, lake, stream, and all with the possibility of having fresh water or salty water. (not talking about oceans) may be shore of a sea will also work. Homework...

An ideal Carnot engine is composed of two reservoirs and a working fluid. The hot Reservoir and the cold one have temperatures ##T_1## and ##T_2## respectively, with ##T_1>T_2##. The working fluid is in a phase transition and has temperature ##T_1## at the start of the Carnot cycle. It undergoes...

Homework Statement why 2/3 is required in this calculation as circled ? I have no idea. I know that 4.5/2 is the distance of the centroid of the bar from point A . Homework EquationsThe Attempt at a Solution

For example, when you are on a rollercoaster and you go past the tip of the coaster you feel like you are going to fly off your seat... however you are radially accelerating down. Same thing when you take a u-turn in a car. you are radially accelerating to your left (atleast in america) however...

Q) two identical smooth balls are projected from points O and A on the horizontal ground with the same speed of projection the angle of projection in each case is 30 The distance between O and A is 100m . The balls collide in mid air And return to their respective points of projection if...

What is the overall moment of inertia of many cylinders in contact, where each is rotated about an axis through its center of mass. For example, a set of rollers. (See picture)

I hope this is in the right thread, I wasn't sure which one to put this in but this seemed like the most likely one to be right, so I'm sorry if this is in the wrong thread. Anyway, my question basically amounts to this: what is the difference between something orbiting around a still planet...

The figure shows a system consisting of two identical spheres of mass m and a mobile platform mass M. If the system starts from rest in the position shown in the figure, what is the speed from each sphere in the moment when both move horizontally, before the crash occurs. Neglect all friction.

How can I identify the direction of a force in finding its moment? :rolleyes:

Purely theoretically, if there were very massive celestial bodies which were not spherical, how would their gravitational warping be? Which shapes would the geodesical paths around them have? Would they still be elliptical orbits or would they have sudden changes of direction? Say for example, a...

I know this sounds like an elementary question with an easy answer. However, I was thinking about chaos theory. Planets and stars are always changing so that their gravitational pulls towards other objects varies. Shouldn't the tiniest change between the pull of a star and a planet, or a planet...

Homework Statement http://tinypic.com/r/vsew5k/8 Homework Equations Angular momentum for rigid bodies Kinetic energy of rigid bodies The Attempt at a Solution I tried to start by using conservation of energy, but I can't find the center of mass of the rod. I'm also not sure where to put the...

Consider a partially filled bottle of water. When it's tipped over and rotating about its pivot point where its edge touches the ground, it has an angular acceleration. Assuming the liquid is not viscous at all, so flows perfectly, at a given instant can it be considered to have a moment of...

Hello, From what I know, internal energy of a body = sum of kinetic energies of the particles of the body + potential energy between the particles (intermolecular forces), right? And there's this textbook question which made me question that for a while: Two objects are at the same temperature...

I read an article on Phys.org (The Strange Case of the Missing Dwarf), and as I'm in the middle of reading and studying Hamiltonian Dynamics, the article made me wonder how the unexplained orbits of existing bodies are used to determine the orbits and masses of as-yet-undiscovered bodies. It...

In practice I’ve found that a valid gravitational model of orbiting bodies only works when the force is computed with only the other mass and not both masses. Thus, the original equation does not work but the modified one does. Is using one mass ok or am I doing something wrong? thanks. [also...

Homework Statement I'm trying to find the point at which FG attracting to the moon = FG attracting to the earth... 5.98e24 kg = Earth Mass 7.35e22 kg = Moon Mass 3.84e8 m = Distance from Earth to Moon Deductions... a = 3.84e8 - b b = 3.84e8 - a a+b = 3.84e8 Homework Equations g = G m / r2...

Suppose I have some sort of rigid body, a solid sphere let's say. For simplicity's sake let's assume that the sphere can only rotate about a single arbitrary axis through the center of mass. If the center of mass of the sphere is traveling with a constant velocity (with respect to some arbitrary...

A 40 km/hr wind is blowing parallel to a storage facility , as shown in the figure. estimate the normal force on a 0.5-m high, 1-m long window if the front door is left open. assume the windspeed along the outside of thewindow is 1.2 U. Air density is 1.22 kg/m^3. There's a picture that...

Homework Statement Given that the force of gravitation between Planet A (the one in the left side of the drawing), Fa=3000/da2 and the force of gravitation between Planet B and the rocket, Fb= 6000/ db2. Assuming that the three bodies involved is in stationary. What are the distances (ranges)...

Hello, this is a question regarding planar physics. Suppose we have multiple bodies. We can ignore their individual shape and angular speed. So every body is represented by it's position, mass and moment of inertia about it's center of mass. Now my question is, how to calculate the moment of...

Homework Statement Three bodies with masses m1 m2 and m3 connected with a string through a sheave with a body with mass m4. The system is moving right. Write the second Newton law for the movement of the objects. Ignore friction. Homework Equations 2nd law for bodies: m4a= m4g-T(the force of...

I just wanted to clear a little doubt of mine. The second law of thermodynamics says that every physical system wants its entropy to be increased, the universe being a physical system should be doing the same. But , then why would two bodies want to attract each other (gravitation) even though...

Can someone either derive or point me to a derivation of Møller's formula for the relativistic minimum radius of a rotating body? I've been searching for about an hour and it's driving me crazy! The only "minimum radius" equation I've seen imposes the speed limit c on a classical rotating body...

Hi there! My physics is not exactly strong (I am a games developer/designer). Basically I have a game idea where the player will jump between the floor and the ceiling. At any point the player will jump and be affected by the gravitational point of the ceiling and the floor at the same...

I mean, isn't the boiling point of water 100 degrees celcius. Even in the hottest of places the temperature does not normally go beyond 45 degrees celcius. So how is all this evaporation taking place?

Background: I'm currently doing a research project on diffusion. I've been thinking about how soluble gases can dissolve at higher concentrations in a colder liquid than a hot liquid. Question: If there are two connected containers, one with hot water and the other with cold water, and the cold...

I am currently researching about the behavior of dark matter and their possible characteristics, and I am needing the individual velocities of the bodies orbiting a center of a galaxy. The collection of data where physicists hypothesized the existence of Dark Matter. Where can I find these data...

Hi everyone. I am not a physicist or scientist but this is a question I have pondered for a while now. Everytime I see a model of how large bodies (eg Earth and sun) bend the planar representation of space (creating a "cup" or "dip") I always feel that this is not completely representative...

I have a question about gravity and the way it interacts with moving bodies. Let's say gravity was the surface of a very stretchy fabric. You take an object like a marble and roll it across an infinite plane of this fabric. The fabric causes the object to lose energy because of friction. My...