Gravitational Definition and 1000 Threads

I understand that GPE is negative, but it does not come out this way when i try to derive it. I took the change in potential energy in bringing a particle from an infinite distance to a distance of b from another particle. ## \Delta U = - \int \vec F \cdot d \vec r ##. Since the...

The derivation of the law have been put up in the forums but I have a question regarding its derivation. I understood everything from the assumptions to the application of Newton's Third Law, but I got stocked at this step: \frac{m}{k} = \frac{M}{k'} . This is similar to \frac{C}{M} =...

I didn't study physics in college nor any other science major, but I love physics and read a lot about it. Still I find troubling contradictions in my understanding of Newton's interpretation of gravity. For starters, how can the force of gravity be directly proportional to the two masses? If...

Homework Statement Relative to space, a spacecraft moving at velocity v in the y direction (y is upwards, x to the right) is getting closer to a planet moving at velocity u in the opposite y direction. The spacecraft does a hyperbolic trajectory with eccentricity sqrt(2) so that it ends up...

Hello. I would like to ask if really gravitational waves (GWs) exist? Mathematically they are predicted to exist. However despites the intense efforts invested to detect them so far they cannot be detected.

I always thought when there is no force acting on an object it moves at constant speed but every object that moves generates gravitational waves what causes that object to lose energy. Does it mean that object loses kinetic energy and slows down and after some (very long) time will stop.

I want to ask the graph of gravitational force against r and gravitational potential energy against r. First, about gravitational force against r The shape of the graph is straight line from origin until the surface of the sphere and then curve (decreasing). I understand about the decreasing...

Hey, I just had the chance to extract the gravitational lensing caused by a massive point using Fermat's principle. I was wondering though, is there any other way to do that? Also is the light's time delation induced by the "refraction index" n (Saphiro delay) connected to "gravitational time...

Homework Statement Please look at the picture. Homework Equations $$F=\frac{GMm}{d^2}$$ The Attempt at a Solution I'm stuck with this problem , because I cannot imagine it properly. If I say that the mass m is in between the two masses , I cannot find d in the choices ,, Any help please!

Homework Statement So I'm calculating the gravitational potential of a sphere at at point P. R = radius of sphere, r = distance from center of sphere to point P. I'm looking at two scenarios; r > R (1) and r < R (2). So I have the following integral: \begin{equation} V(r) = \int...

Do particles popping in and out of existence due to quantum vacuum fluctuations create a gravitational effect? My thought is yes If so, considering all the quantum particles in existence at one time at a given moment in the universe, added to the mass of the universe as well as the mass of...

Homework Statement This is just a project for fun, not homework. I'm writing something in python that takes in an apple's initial position vector and initial velocity vector, and for a given gravitational field due to a planet, returns the next position vector after a small time increment...

1. A satellite is revolving very close to earth. what is the % increases in velocity needed to escape from the gravitational field of earthHomework Equations v= root gh The Attempt at a Solution Sorry, i don't have any solution .

I see that the formula for hawking radiation is related the the formula for unruh radiation. The accelleration experienced by a body yields an unruh temperature equivalent to a black holes hawking temperature with an equivalent value of g. The unruh effect happens at all accelerations, therefore...

Homework Statement Two solid copper spheres of radii 1 and 2 cm are released from rest in free space, their centers being 20 cm apart. Estimate the velocity with which they collide Homework Equations density =mass/volume F=GMm/r^2 The Attempt at a Solution Find mass of each from density of...

What is a gravity tidal torque on a simple circular ring, inclined at some angle i? I can't find a solution for this simple problem, despite the ring's idea is frequently used in the precession problems, for example in the Earth's axis precession case. How this can be computed effectively?

I have read that the team at Vienna are conducting experiments to test whether even gravity can exhibit quantum superpositions or not. Is anyone tracking their late developments on this? What do the physics community think is going to happen when even gravitational waves are superposed. Will the...

Homework Statement A quasar at redshift 0.3 is gravitationally lensed into two images by an elliptical galaxy at redshift 0.18. The two images of the quasar are separated from the center of the galaxy by 1.1 and 1.6 arcseconds, on opposite sides. One of the quasar images flares up in intensity...

Has anyone got any experience of this using a dual axis sensor on a pendulum? I have attempting to do itt however I am not completely satisfied that my method is successful

I got a question from my exam. We are given the name of three fields; electric field, magnetic field and gravitational field. A charged particle is placed in a field, but no force will act on it if it's stationary or moving in any direction. What field is the particle placed in?

Consider a solid globe of mass M and of of uniform density. My understanding is that its external gravitational field, in the absence of any other forces, will apply an instantaneous acceleration to any small test mass directly towards the center of the globe. Is that still true in the...

I've seen many sci-fi that they said wormhole could be detected by its gravitational wave ? Does wormhole actually create gravitational wave ? And how could a pair of black hole spinning around each other create such thing as gravity wave ? I am sorry for lacking knowledge about general relativity.

The Gravitational Binding Energy of Earth is 2 * 10^32 J. But the total mass energy of Earth is 5.4 *10^41 J. So the shatter the planet into pieces it would require 2*10^32 J of energy, and to completely destroy the planet without leaving a trace of its existence would require 5.4 *10^41 J right?

Hey Guys! I've been doing a few equations in regards to planetary escape velocity and gravitational force. The below links have the escape velocity of listed planet on the left side of the board, the gravitational force between the Sun and given planet on the right side. In the middle of the...

Hello , my question is : If we could observe a planet life so far away from the Earth with so much gravity that it makes time pass more slowly on that planet , what would we see? Like what can we say about motions of lifeforms living on that planet? Would they be moving in slow-motion in the...

Homework Statement Forty 2.0kg blocks 20.0cm thick are used to make a retaining wall in the backyard. Each row of the wall will contain 10 blocks. You may assume that the first block is placed at the reference level. How much gravitational potential energy is stored in the wall when the blocks...

I am working on a problem to sate my own curiosity. :) My mass is approximately 85.1 Kg. The Earth's mass is approximately (5.972x10^24 kg) and the distance between our center of masses is roughly the same as the Earth's radius of (6371 km) so I was wondering; what would the Earth's...

Suppose we have a large circular disk with pegs around the perimeter, and we set the disk rotating so that one pegs passes us every second. Then, we move this disk to a gravitational field, such that one side of the disk is closer to the gravitational mass than the other. From our perspective...

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)...

Is a one-dimensional gravitational field possible? I'm not sure if I'm using the correct terminology, what I mean is instead of pulling things into its center of gravity it pulls things in the same linear direction until it ejects it out.

Gravity has such a long range and such a weak magnitude . Might it be due to the fact that it's acting on the three-dimensional vehicle as a mode exerting its force this way gives limitations, its inability to conserve energy due to friction resistance among others. Also is gravity applied...

Homework Statement Homework Equations g = GM / r^2, where g is the gravitational field strength, G is the gravitational constant, M is the mass of the attracting body, r is the radius of the attracting body. p = M / v, where p is density and v is the volume. Vs = 4/3 * pi * r^3, where Vs is...

I found http://physicspages.com/2013/05/05/schwarzschild-metric-gravitational-redshift/: \frac{\lambda_R}{\lambda_E} = \sqrt{\frac{1-2GM/r_R}{1-2GM/r_E}} where the indexes R and E are for receiver and emitter respectively, and the speed of light is normalized to 1. Most other sources on the...

I tried to get the potential from the potential energy and I get a positive sign for potential...! I cannot find what I did wrong. - Gravitational force is conservative so its work W is symmetrical to the change in potential energy U. - Potential is the work done by gravitational force, per unit...

Hi. In class, the professor has tried to derive the equation by using the principle of least-action. (But not yet completed. Maybe next class...) However I heard this method is used by Hilbert, who had derived the equation 5 days before Einstein derived it. Then, what method did Einstein use...

Hi, Just curious if anyone knows of a formula that would show how mass changes in a gravitational field? I have seen the formulas for gravitational time dilation and length contraction (which are rather similar) and was wondering is mass changes the same way. Thanks

Homework Statement Homework Equations g = G*M / r^2, where g is the gravitational field strength, G is the gravitational constant, M is the mass of the attracting body, r is the distance from the center of mass of the body. V = -G*M / r, where V is the gravitational potential. The Attempt...

Homework Statement A student holds a book at rest on the palm of her hand. She lifts the book straight up, bringing it to rest again at a higher point. 1. Is the net work done on the book positive, negative, or zero? 2. Is the change in the gravitational potential energy positive, negative...

Homework Statement The gravitational acceleration at latitude x (0<x<90) can be estimated with g(x)=a*cos(2x)+b. 1) Determine what a and b is if the gravitational acceleration is 9.780m/s^2 at x=0 and 9.832m/s^2 at x=90. Homework EquationsThe Attempt at a Solution So I begin by entering what...

Homework Statement A 12 kg meteor experiences an acceleration of 7.2 m/s^2 when falling towards the earth. a) How high above the Earth's surface is the meteor? b) What force will a 30 kg meteor experience at the same altitude? Homework Equations Fg= Gm1m2/r2 m1m2 r2 = Gm1m2/Fg r =...

Have "we" (the scientific community) found any proofs of gravitational waves? I read about an experiment including a couple of mirrors very apart from each other and a laser that aimed to somehow measure the possible existence of gravitational waves, but as far as I understood (clearly not much)...

Desloge (1989) published the article: ## '##Non-equivalence of a uniformly accelerating reference frame and a frame at rest in a uniform gravitational field## '##. His result, briefly resumed: a uniform gravitational field is not flat, is quite interesting. But the way he proves the result is...

Homework Statement Calculate the maximum gravitational attraction between a man and an apple, when a) the apple was 1m from the man's center of mass, b) the apple hit his head. (man's mass 60kg, apple mass 100g) Homework Equations F=G(m_1)(m_2)/r^2 F=ma The Attempt at a Solution I set up the...

Hi, I need a beginner's book to study gravitational waves by myself. I am an undergrad physics major and just took my GR course. A beginner's book on GR will also help me lot. please suggest

Homework Statement Alice and Bill are at the top of a building. Alice throws her ball downward. Bill simply drops his ball. Which ball has the greater acceleration just after release? Homework Equations force, F=ma and F=mg The Attempt at a Solution Alice: F=ma+mg=m(a+g) Bill: F=mg...

Homework Statement A large telescope of mass 8410 kg is in a circular orbit around the earth, making one revolution every 927 minutes. What is the magnitude of the gravitational force exerted on the satellite by the earth? M_E = 6.0x10^{24} kg m_s = 8410 kg T_s = 927 min = 55,620 s G =...

Is this established or is it dependent on the size of the black hole? http://www.space.com/22180-neutron-stars.html Neutron stars pack their mass inside a 20-kilometer (12.4 miles) diameter. They are so dense that a single teaspoon would weigh a billion tons — assuming you somehow managed to...

Is the change in frequency an actual change or is it like the Doppler effect? Does the speed of light also change in a g-field?

I thought I know introductory physics well but now I'm confused about simple things! Imagine a pendulum. Its released from rest from a height. We take that height to be the zero level of the gravitational potential. But that means its total energy is zero at the beginning and because of the...

As I'm sure I've mentioned before, I've heard people say that stress and pressure terms in the energy tensor act as a gravitational source, but I don't understand how this could be, given that these terms can simply appear or disappear (in a non-stationary situation), unlike energy and momentum...