Gravitational Definition and 1000 Threads

Homework Statement Halley’s Comet orbits the sun about every 75 years due to the gravitational force the sun provides. Compare the gravitational force between Halley’s Comet and the sun when the comet is at aphelion (its greatest distance from the sun) and d is about 4.5 x 10^12 m to the force...

One of my students asked if the graviational force at the Earth's centre is zero. The question was thrown open to the other students and two possible answers were given: zero or infinite! One way of reasoning is to say that the graviational force sums to zero as (assuming uniformity of the...

Homework Statement Question :- Two stars, each of a solar mass and radius ##10^7 m## are at a distance of ##10^{12} m## from each other. Find the speed of each star before collision if initial speed is negligible. Homework Equations $$V(r) = {-G Mm \over r}$$ The Attempt at a Solution...

Gravitational potential energy between 2 objects is ##-{G\times M\times m\over R}.## My question is, does the value of this equation of this equation mean total gravitational potential energy of both objects ? i.e, say the gravitational potential energy of object with mass ##M## is ##p## and...

Homework Statement What is the gravitational potential both inside and outside a spherical shell of inner radius b and outer radius a? Homework Equations φ = ∫g⋅da = -4πGMencl g = d∅/dr in the r hat direction The Attempt at a Solution I can get as far as getting the gravitational field for...

https://www.ligo.caltech.edu/video/gravitational-waves How do gravitational waves get emitted here? Is it in a sphere or on a flat(?) surface?

Homework Statement A teeter toy is composed of a massless central stick of length L and two massless sticks of length l attached at angles α, each with a mass m at the end (see the figure). We imagine tilting the toy by an angle θ from the upright position. a) Find an expression for the...

(Sorry for my bad English.) Suppose we choose the surface of the Earth at a point as having a zero potential energy. Now if there're two particles of equal mass at rest, one of them just an heigh above the another, the one which is at the ground will not have potential energy. Since the...

Is it possible for enough energy to be dissipated in the form of gravitational radiation in a two-body system to allow for capture? From what I remember, you would need extremely massive bodies passing extremely close to each other: I'd like to know how massive and how close. It has been a few...

I have a question about why the duration of the gravitational wave signal detected by LIGO was 0.25 seconds or so. I think I understand correctly that as the two binary black holes rotate around each other and move closer together there is a loss of angular momentum that is converted to...

IIRC , a perfect sphere will not be detectable with a gravitational detector, but an ovoid shaped body will, why is this so? or am i wrong.

I am curious as to the formula for radiative power due to a single object in forced circular motion. In particular, I am interested in the power of gravitational radiation for volumetric invariant mass densities for both the low density Newtonian limit and the high density general relativistic...

Homework Statement "In Fig. 8-33, a runaway truck with failed brakes is moving downgrade at ##130\frac{km}{h}## just before the driver steers the truck up a friction-less emergency escape ramp with an inclination of ##θ=15°##. The truck's mass is ##1.2⋅10^4kg##. What minimum length L must the...

So I was reading that the equivalence principle of Newton doesn't work because of a thought experiment. They said that an experimenter shoots bullets( 1 per second) from the bottom of the elevator to the top. This happens in outerspace where the elevator moves up with accleration g. And this...

When a wheel spins does it generate lift or something, the wheel spins so that the torque force is downwards. for example you measure the weight of the wheel and then you spin then wheel does anything change? The wheel is solid and if their change something does it matter if it is a constant...

I have some questions about the first discovery paper that was released about gravitational waves, especially some of the maths. How did they: 1. Calculate the masses of the black holes that merged 2. Calculate the energy radiated away in gravitational waves 3. Calculate how far away the event...

<<Mentor note: Moved from this thread>> I read this article http://thedaily.case.edu/rotating-galaxies-distribution-normal-matter-precisely-determines-gravitational-acceleration/ It claims that the rotation of galaxies can be explained without a need for dark matter. I not an educated...

Homework Statement Consider a particle in a gravitational field that is also subject to a resisting force proportional to the velocity squared ( Fdrag = + or - cv2). a) Find the terminal velocity, vT, for the object as it falls. b) Show that for an object dropped from rest that the velocity...

1. A comet that passes by Earth has GPE, which will be all lost if it begins to fall towards Earth. If it's shot back up, it will now start with Ek and finish with a higher GPE. Now, what exactly is this GPE? if energy cannot be created or destroyed, but transformed, where does it get stored at...

What would happened if the speed of gravitational waves were not equal to the speed of light . Please explain it with example of sun and Earth or any other but in easy way. With reference to general relativity.

Hi all, On the subject of being able to feel gravity waves as a human without machines, I couldn't find a very definitive answer to what I was looking for. First, I reference the video: at 40 tp 55 seconds. Its called: LIGO, journey of a G wave. They say in this clip that when the black...

Hello. I have a theoretical doubt about the gravitational time dilation in the particular case of the acceleration in regard to the scenario of a planet in which the pass of the time is faster than in the Earth (e.g., a planet X where a year is equivalent to a second in Earth) . The fact of...

Why gravitational force is attractive? Some where it was written that gravitons are hypothetical particles which mediates the force of gravitation, and it has a spin of 2 , and Quantum field theory had proved that any particle of spin 2 characteristic will always mediate attractive force...

I was trying to solve this excercise: Now I was able to find the eq. of geodetics (or directly by Christoffel formulas calculation or by the Lagrangian for a point particle). And I verified that such space constant coordinate point is a geodetic. Now, for the second point I...

Hi there. Have been doing some informant l independent research on gravitational lensing. It turns out that all einstein runs are blue. Why Is this?

I have never had to use the English Engineering System so I am having a bit of a struggle here. I understand the concept of an inconsistent system of units. I understand the following 2 statements: 1lbf = 1lbm x 32 ft/sec^2 1lbf = 1slug x 1 ft/sec^2 When given a problem that is asking for the...

I have read that: In 1915 Einstein presents to the Prussian Academy of Sciences the General Theory of Relativity; it includes a set of Gravitational Field Equations; at this time he does not present any solution to the equations. In 1917 he considers a greatly simplified case; presents a...

I know that gravitational potential due to uniform sherical shell at a point outside the shell is equivalent to the potential due to particle of same mass situated at the centre and got proof here http://m.sparknotes.com/physics/gravitation/potential/section3.rhtml. But I was looking for more...

By reading on the internet I ve found various websites talking about the relation between gravitation and electromagnetism, and in particular, under: - "Small" Gravitational fields -"small" changes in energy with respect to time, The linearized enstein' s field equation becomes pretty much...

I know that when an object A a does positive work on another object B, object A loses energy and object B gains energy(there is transfer of energy from object A to object B) and when object A does negative work on object B, it gains energy and object B loses energy(there is transfer of energy...

Sci Am August 2016 discusses a supervoid detected in the direction of the CMB cold spot. The analysis assumes the gravitational potential is less in the center of the void than near its edges (thus near its surrounding galaxies). On the other hand the gravitational field inside a spherical...

This is a quote from an article written by a Phd student in physics in the online magazine Aeon (https://aeon.co/ideas/gravitational-waves-will-bring-the-extreme-universe-into-view): "Consider the properties of the September 14 event: the signal was generated by two objects, each roughly 35...

I understand gravitational waves as ripples in spacetime. As PeterDonis said in an earlier post, " The 4-d spacetime geometry does not have to "propagate" anything; it just is." On the other hand, this is block-universe speak. In this language, verbs that imply change are forbidden. We might...

If the amplitude of gravitational waves, frequency of gravitational waves and the vector potential of magnetic field in surrounding of such waves are known then what would be the easiest way to calculate resultant acceleration of electrons? My above question is based on the various researches...

Hi all, I am currently reading 'The Science of Interstellar' by Kip Thorne. Kip says that cooper could navigate around the Gagantua system using Gravitational Slingshots with Intermediate-Mass-Black-Holes. However these interactions would accelerate/decelerate the ranger by up to 22% of the...

Hi when i found out about the presence of gravity waves, i first thought 'what happens if they were to be reversed' and then i thought 'what happens to space time in between these waves?' thanks

Book: Landau Lifshitz, The Classical Theorey of Fields, chapter 11, section 95. I have gone through the derivation of Einstein field equations but not without holes to fill and fix in my understanding. Let's start with the action for the grtavitational field ##S_g## which after some explanation...

Physics Videos by Eugene Khutoryansky (a widely respected channel) recently posted a video on YouTube suggesting this. I know that gravitational fields cause time dilation (with time passing more slowly the closer an object is to the centre of gravity, relative to more distant observers), but...

Electromagnetic wave behaves like a harmonic oscillator. Similarly a photon behaves like a quantum harmonic oscillator. http://www.physics.usu.edu/torre/3700_Spring_2015/What_is_a_photon.pdf ##dA/dt## and ##A## behaves like ##dx/dt## and ##x## at a harmonic oscillator. I suppose that...

Would someone please explain what this quote is saying? What does it mean when they say that spacetime locally reverts to the vacuum? Wasn't the passing gravitational wave made of spacetime vacuum to begin with? And what about the detectors not returning to their original relative position? Is...

I am currently reading Gravitational Curvature by Theodore Frankel. In the derivation of Einstein's equations in chapter 3, he states that the gravitational potential energy of a blob of fluid is ∫B½p0U√gVdx where the integral is a volume integral, p0 is the rest energy density and √gvdx is...

Hello, was just wondering, what determines the gravitational orbit of an object orbitting a planet, for example, Saturn. Would increasing the size of the object decrease the distance between the object and the planet? Also, what determines the speed at which anything moves throughout it`s...

Homework Statement A body of mass m is taken at a constant speed from the surface of the Earth (radius = Re) to infinity. (a) What is the work W1 done on the body in the process? (b) If m is taken from a distance r > Re to infinity, how much work W2 is required? (c)Which quantity is larger, W1...

Hi. A student wishes to test gravitational time dilation near a black hole within her lifetime, so she travels to a location where a black hole is said to reside and parks her ship at distance where she is not affected by the hole's time dilation effects. She then fires a tethered capsule...

Homework Statement The problem is attached Homework Equations Energy, gravitational formulas The Attempt at a Solution For part b, the answer is 2km s^-1 If it can escape, KE-PE(energy traveled from infinity to R)=0 KE = PE mv^2 /2 = GMm/R v^2/2=GM/R..(1) I tried to find GM by using the...

Homework Statement What is the gravitational field strength at a point 6.38x106 m above the Earth's surface? Homework Equations The Attempt at a Solution Ok so I plug in all the known variables. G= 6.67x10-11. M= 5.98x1024. r= 6.38x106 and so I multiply that by 2 because the given point is...

Let's say there's a massive and uniform sphere of radius, r, and there's a box in its gravitational field and the sphere is so massive that the box is accelerated to a velocity near the speed of light; could the classical coordinate system still be used or is the Schwarzschild coordinate system...

So we know that in GR electromagnetic waves have their trajectories effected by the gravity of stars and planets. But how about gravitational waves. Are their trajectories altered by gravity? If so, would this imply that gravitons are self-interacting if they exist?

What happens to the normal reaction of the force of gravity on a body orbiting around the Earth? The force of gravity provides the centripetal force, but does all of it get converted to centripetal force? Is there any kind of resultant force towards the centre of the Earth (due to the normal...

Hi I am new to the forums. Only undertaken basic physics. Had a thought the other day and wanted to share it. Is lensing of starlight such as einstein rings ever caused by refraction? Could a matter density gradient theoretically cause the same effect? Thanks guys Sorry if its a repost...