Gravitation Definition and 918 Threads

I have been trying to understand the implications of a thought experiment and am interested to know either where it's going off course or what those implications might be. Through some reading of earlier threads on this forum I have verified my starting hunch that photons bend spacetime despite...

Homework Statement earth has a mass of 5.98x10^24 kg and the moon has a mass of 7.35x10^22 kg. The distance from the centre of the moon to the centre of the Earth is 3.84x10^8 m. A rocket with a total mass of 1200 kg is 3.0x10^8 m from the centre of the Earth and directly in between Earth and...

Suppose we have Einstein equation for *Universe free of matter* in form \begin{equation} G_{ik} = \chi T_{ik}, \end{equation} where the cosmological constant $\Lambda$ is transferred to the RHS of equation and written in the form of stress–energy tensor of Dark Energy...

I have a simulation I'm trying out (for fun). A self-gravitating ball of gas, in deep space. (The sim uses a fixed-time-step for each iteration.) I'd like to use Boyles Ideal gas law, the force of gravity, and energy as internal heat. (I don't want to touch enthalpy unless I don't realize...

In the universe, there are several celestial bodies, all of which attract each other. Then why is it so that they do not collapse towards each other. Is it a consequence of expansion. If so, will a change in acceleration of expansion have any effect on it.And can then this be considered a...

Homework Statement A pendulum having a bob of mass ##m## is hanging in a ship sailing along the equator from east to west. If the ship sails at speed v what is the tension in the string?. Angular speed of Earth's rotation is ## \omega ## and radius of the Earth is ## R ## Homework Equations...

Homework Statement Homework EquationsThe Attempt at a Solution I think : the question means that almost all of the potential energy gets used into the explosion. If this is true then the potential energy gets reduced by ## \frac { GM^2} R ## or if the star just gets transformed into a...

I am having a problem with visualizing why Newton's Law of Universal Gravitation (NUGR) holds true when objects get close together. F=Gmm/r^2 makes sense for planets that are far away because each object can be treated as a point with gravity acting at the center of each object. For a person...

The classic book on General Relativity by Wheeler, Thorne and Misner is now out: https://www.amazon.com/gp/product/0691177791/?tag=pfamazon01-20 I got to use preprints of the book while doing an independent study of General Relativity in 1973. It brings back fond memories of being tortured by...

Hello Everybody, I am Meaningless and I had this doubt on Newtons laws of gravitation while deriving it. My textbook stated the following derivation 9 for any two masses m1, m2, and radius 'r' It stated that according to the law of product of masses...

Homework Statement A particle of mass m is dropped from a height h, which is not necessarily small compared with the radius of the earth. Show that if air resistance is neglected, the speed of the particle when it reaches the surface of the Earth is given by ##\sqrt {2gh}## ##\sqrt {\frac {R_E}...

TL;DR Why does the Einstein equivalence principle imply that all forms of (non-gravitational) energy source curvature? Now, as understand it, the Einstein equivalence principle (EEP) implies (or at least suggests) that gravity is the manifestation of spacetime curvature, the reason being that...

Homework Statement consider the motion of a comet in an elliptical orbit around a star. the eccentricity of the orbit is given by e= 0.20 and the distance between the perhelion and the aphelion is 1.0 × 10^power8 a- find the distances of nearest and farthest approaches of the comet. b- if the...

I was wondering if it is possible to use only a stopwatch and a telescope to find the mass of a planet, such as Saturn. I've experimented with a couple of things but I keep running into problems. I previously asked this question in the homework section, but it does not involve numbers, is not...

Homework Statement Using only a telescope and a stopwatch, find the mass of Saturn.[/B] (This question may or may not make any sense at all, it was a theoretical lab that my professor said without giving us a chance to copy it down and I am trying to recall the question from memory) If it is...

Hi! With the re-release of the textbook "Gravitation" by Misner, Thorne and Wheeler, I was wondering if it is worth buying and if it's outdated. Upon checking the older version at the library, I found that the explanations and visualization techniques in the sections on differential(Riemannian)...

Homework Statement 4 10kg objects are located at the corners of a rectangle sides 2 meters and 1 meter. Calculate the magnitude of gravitational force on 1 due to the other 3. (Same sort of idea) 3 1kg objects are located at the corners of an equilateral triangle of side length 1 meter...

In another thread I posted this graphic, How does this picture above need to be modified to include gravitation if possible? What does the M+ and the M- represent? Is there a place for the Higgs particle in the above picture? Could the above picture be turned into a movie and show say an...

Homework Statement Matt Damon is stuck on Mars. He needs to get o the planet and into orbit to rendezvous with the rescue team, which will be orbiting the planet at the same radius as Phobos, one of Mars’s moons. His goal is to determine what his take-of speed should be so that he makes it into...

Hello, I don't know if this is the right place to post this topic, I could not figure out the right one. I have recently finished my Masters in Condensed Matter. Now I want to follow a PhD where I can work/research on the dynamics of the Universe especially on dark energy, modified gravity...

The Feynman Lectures on Gravitation is a famous book. There are originally 27 lectures but only the first 16 has been published. The remaining 11 lectures can only be found in the first edition (1962-63). It is very rare but is there a (possible) way to read the content, provided that my...

When we heat something then it breaks and it is due to the transfer of energy . But what if we ignore the energy and thought it as Force I.e. the object molecules break due to Force applied on each other ( molecules) . So is it right to say heat apply Force.?

One way to get the universe to expand is with dark energy that pulls at the matter of the galaxy separating it or equivalently for space-time to not be perfectly flat. An alternative, in principle, would be for the gravitational pull between objects like galaxies and galactic clusters to be...

Homework Statement Two fully equal sphere's of lead are placed next to each other so that the gravitational force between sums up to 10N. Calculate mass and radius of the two sphere's. F=10N , ρlead=11300kg/m2 Homework Equations F=gm, F=GMm/r2 , V=4πr3/3 , ρ=m/VThe Attempt at a...

I had this discussion while driving home to California from a trip to Washington state with a friend. We were discussing the stability of a completely rigid, untethered, ring-structure around Earth, and I did not know how to explain to him that such a thing must be tethered by rigid towers lest...

My question is, take Mars, say, and install a huge rocket engine on the ground pointing out the planet (obviously) and in the opposite direction of its velocity, so that if it is turned on, the planet is slowed. The rocket starts to work and Mars is slowed. If the loss of velocity goes little by...

It seems that with the 2016 LIGO and VIRGO confirmation of the gravitational chirp that we have also experimental confirmation that the speed is indeed the speed of light. True? https://en.wikipedia.org/wiki/First_observation_of_gravitational_waves#Direct_observation

In Weinberg's book, it is said that a given metric ##g_{\mu \nu}## could be describing a true gravitational field or can be just the metric ##\eta_{\alpha \beta}## of special relativity written in curvilinear coordinates. Then it is said that in the latter case, there will be a set of...

There's a question that's been in my mind for quite a while but I cannot figure out what the answer is. I't probably an ill posed question but I will ask it anyway: 1.- Do we know what the dark-matter statistical distribution in our Universe is (at large scales)? 2.- In case we do, could...

Well, first of all i want to apologize about my english skills hahaha I have been trying to calculate a time formula for free falling object through large distances (or weak gravitational fields) and my results don´t have much sense (I test my results in a quite realistic game called Algodoo)...

Homework Statement [/B]Hello, I have derived the equation for the gravitational force for a disk to be 2Ggm/a^2(1-x/sqrt(a^2 - x^2) when an object is added on top of the system. My question is would the force still be somewhat similar if the disk now had a small hollow of radius c...

Why is gravitational force equal mass multiply gravitational acceleration F=m.g

Homework Statement A projectile is fired vertically from the Earth's surface with an initial speed of 11.4 km/s. Neglecting air drag, how far (in meters) above the surface of the Earth will it go? Homework Equations (1/2)mv^2 -GmM/R The Attempt at a Solution KEi+PEi = KEf+PEf (1/2)mv^2 -...

Homework Statement A comet moves around a stat in ##xy## plane along elliptical orbit, described by $$ 0.16 x^2 + y^2 = 4 $$ where ##x, y## are in ##AU## 1) Sketch the comet in the ##x,y## coordinate system denoting all orbit parameters 2) Find the semi major and minor axes of the orbit...

I recently studied about black holes and hiw they attract light too. But does light have mass? If it doesn't, I don't see any way how gravitational forces affect light. I have heard a bit about wave particle duality. But could you make it more clearer? I have no idea of relativity or particle...

Years ago I read an article illustrating the vastly different strengths of the electromagnetic and gravitational forces. The article gave a figure for the number of excess electrons dispersed throughout the Earth that it would require to overcome the gravitational binding of Earth's matter and...

I recently put together a simple 2D gravity simulator and I'd like to get some feedback or suggestions you may have for future updates. I'm planning to make a 3D version and improve the animation (framerate, realism, etc). This first simulation includes the Sun, Mercury, Venus, Earth, and Mars...

Hi, judging by the TOC and the free preview of chapter 10 on Springer's website, this book seems a great supplementary read for a regular (undergraduate) classical mechanics or astronomy course. https://www.amazon.com/dp/1461454433/?tag=pfamazon01-20 Newton's Gravity: An Introductory Guide to...

Hi guys. I hope Scientists are at the same time civilized. Because science is civilization. Firstly I'm sorry about language. In Turkey, Our education system does not adequately support English. Anyway. What is the evidence about gravity is exist. Wait. I mean, we know something pushing...

This thread is to serve as both a compilation and ground of discussion of key experiments, both historical and planned, which attempt to probe possible macroscopic limits of QM, taking into account e.g. some particular gravitational/optical/mechanical/superconducting/etc aspect and/or...

Are they the same object?

I am given the solution to the first part of the problem, however not the second part - would appreciate for someone to double check my work! Cheers. 1. Homework Statement If a scale model of the solar system is made using materials of the same respective average density as the sun and...

Hello everyone 1. Homework Statement In the solution of a question, regarding the gravitational force fields and gravitational potential when the mass is inside Earth (where the height of the mass is lower than the radius of earth), the step where we take the integral of the force in order to...

Homework Statement Scientists are planning to launch a rocket from the surface of the Earth into an orbit at a distance of 18000 km above the centre of the Earth. The radius of the Earth is 6400 km and it has mass 6.0x10^24 kg. What is the minimum work done to move the 150kg mass of the rocket...

Homework Statement There are a big object and an astronaut in space. How do we calculate the gravitational force between them. I enclose a photo. I have given the mass of an astronaut, the dimensions of this giant ring and density of the ring. There is also a mistake in the photo. The astronaut...

a satellite is in circular orbit around the sun. which requires a greater change in speed: the satellite to fall to the sun or to escape the solar system Homework Equations f = gmm/r^2 The Attempt at a Solution Calculated the escape velocity as(2 GM/R)^0.5 how do i find the speed required so...

Homework Statement Find the total time, t, that an object takes to reach the surface of the Earth from a distance, D, using the Law of Gravitation: $$F_{g} = \frac{GMm}{x^2}$$ R is radius of Earth D is distance from surface R+D is total distance from center of masses ****** One Dimension...

Homework Statement (a) The Earth may be considered to be a uniform sphere of radius 6.37 × 103 km with its mass of 5.98 × 1024 kg concentrated at its centre. The Earth spins on its axis with a period of 24.0 hours. (i) A stone of mass 2.50 kg rests on the Earth’s surface at the Equator. 1...

Homework Statement Derive E=mgh from Newton's law of Gravitation where h is very small. (Use binomial expansion) 2. The attempt at a solution E = \frac{GMm}{(r+h)^2}-\frac{GMm}{r^2} E = \frac{GMm}{r^2}(\frac{1}{(1+\frac{h}{r})^2}-1) E = \frac{GMm}{r^2}((1+\frac{h}{r})^{-2}-1) E =...

Homework Statement Comets travel around the sun in elliptical orbits with large eccentricities. If a comet has speed 2.2×10^4 m/s when at a distance of 2.6×10^11 m from the center of the sun, what is its speed when at a distance of 4.2×10^10 m Homework Equations L = rp = r(mv) The Attempt at...