Gravitation Definition and 918 Threads

Homework Statement i have 2 questions on my holiday homework that I am not 100% sure on they are: Homework Equations 1) write down an algebraic expression for g at a distance r from the centre of the planet. The planet can be treated as a point mass of magnitude M as its centre AND 2) write...

Homework Statement It is a problem on gravitation of MTW pg 65 excercise 2.5. A particle of rest mass m and 4-momentum is examined by an observer with 4 velocity u. Show E=-p*u under -1,1,1,1 metric Homework Equations Treating c=1, we have u*u=-1 and p=m*u. The Attempt at a...

Homework Statement You weigh 518 N at sidewalk level outside the World Trade Center in New York City. Suppose that you ride from this level to the top of one of its 410 m towers. Ignoring Earth's rotation, how much less would you weigh there (because you are slightly farther from the center of...

I recently watched a video by SpaceRip on YouTube addressing whether or not the Universe is infinite. They mentioned an example as to why it isn't briefly, but didn't expand on it. I kept thinking that its a good reason and I want your opinion on it. Since Newton's law of universal gravition...

Hey, everyone, I'm new here. I signed up to get an equation that I would really like to find, but I've been searching for a few days and haven't found anything that helped. What I'm wondering is how to find the force between two magnets. Once I have that equation, I'll ask another one that I...

Hi. I would like to learn the mathematics from Gravitation by MTW, but i find the book hard to follow mainly due to its style. Many other authors seem to work mainly with components and do not employ the exterior derivative etc. Does anyone know some text which treats GR similarly to MTW, but...

We very well know how to calculate curvature in gravitation. But this time i just need a physical explanation to this question on my mind: "In order to describe n dimensional space with constant curvature why do we need to go to n+1 dimensional flat space? Why don't we use just n-dimensional...

On occasion I notice there is some talk about "graviton" particles, I would have thought astro/ quantum sciences were past that idea. I am quite aware of a basic rule "Don't fall in love with your theories" so a gravity particle might exist, more on that later. In my understanding of...

How do gravitons mediate the force of gravitation in universe ?

Hi, guys. I was wondering on Newton's Gravity Law derivation, and I found this page: http://www.relativitycalculator.com/Newton_Universal_Gravity_Law.shtml Everything seems clear, but the first step is just killing me, because I can't get it. Assuming small incremental changes in s...

Homework Statement https://aapt.org/physicsteam/2010/upload/2009_F-ma.pdf Homework Equations L = mrv L = Iω The Attempt at a Solution For a circular orbit: Fc = Fg mv^2/r = Gmm/r^2 v = √(GM/R) Thus: l = mR√(GM/R) l = m√(GMR) This means that LA > LC, eliminating choices B...

Homework Statement A spring system is set up as follows: a platform with a weight of 10 N is on top of two springs, each with spring constant 75 N/m. On top of the platform is a third spring with spring constant 75 N/m. If a ball with a weight of 5.0 N is then fastened to the top of the third...

Scenario 1: A small mass is moving away from a large mass, slows down, reverses direction such that at t=0 it has an instantaneous velocity of 0 wrt height r. Scenario 2: An identical small mass is moving directly toward the large mass such that it arrives at height r with a velocity relative...

Author: Charles W. Misner, Kip S. Thorne, John Archibald Wheeler Title: Gravitation Amazon Link: https://www.amazon.com/dp/0716703440/?tag=pfamazon01-20 Prerequisities: Level:

I was going through a site which tells: F=G.m1.m2r^2 Also F=-G.m.m/r^2. Can it be written? Thanks.

Hello, The gravitational binding energy of a system is equal to the negative of the total gravitational potential energy. Is this given by the equation: U=-alphaGM^2/R where alpha=3/5 and the equation stands as: U=-3/5GM^2/R? Kindly correct me if I am wrong?

Hello, Can anybody please explain me: While going through gravitation potential energy, I came across: F=G.m1.m2/r^2 From there it follows: g=-GM/r^2.r How does it follow? Specially the -G case? -- Shounak

Hello, Can someone please explain me: F=G m1xm2/R^2 In potential energy U=mgh Generally it is also written that: U=-Gxm1xM2/r+K. How -G comes into play? Also Newton's above law of Gravitation in vector form is written as: F_12=-Gm1m2/r12^2 r12 Here also how -G comes into...

Homework Statement Two satellites are launched at a distance R from a planet of negligible radius. Both satellites are launched in the tangential direction. The first satellite launches correctly at a speed v0 and enters a circular orbit. The second satellite, however, is launched at a speed...

Can anyone give me a situation when the gravitational potential due is 0 but gravitational field is non-zero.

Homework Statement A spherical shell has inner radius R1, outer radius R2, and mass M, distributed uniformly throughout the shell. The magnitude of the gravitational force exerted on the shell by a point particle of mass m located a distance d from the center, outside the inner radius and...

Homework Statement At the Earth's surface a projectile is launched straight up at a speed of 8.1 km/s. To what height will it rise? Ignore air resistance and the rotation of the Earth. Homework Equations F = GMm/r2 Ug = -GM/r2 G = 6.67 e -11 whatever units it happens to be That's all...

Homework Statement The Earth orbits around the sun because it has angular momentum. If we stopped the Earth in orbit and then let it fall straight towards the sun, how long would it take to reach the sun in seconds? Details and assumptions The mass of the sun is 2×10^30 kg. The mass of the...

Homework Statement What is the distance from the Earth's center to a point outside the Earth where the gravitational acceleration due to the Earth is 1/10 its value at the Earth's surface?Homework Equations FG= GmM/r^2 g= Gm/r^2 G=6.67x10^-11 (Nm^2)/kg^2 m(earth)=5.97x10^24 kg g=9.8m/s^2 The...

Hello, can I calculate the pression of the atmosphere at a certain height using the gravitational law ? thank you

Homework Statement A spacecraft orbiting the Sun uses its jet engine for slowing down its orbital rotation and changing the direction of its velocity. At the moment when the velocity is directed away from the Sun and has a magnitude of v = 30 km/s, the jet engine is switched off. At the same...

Homework Statement an object of mass 750 kg is lifted from the Earth's surface to a height of 6.8 x 10^6 m above its surface. Calculate the change in gravitational potential energy for the object. The Attempt at a Solution I used this formula ΔEg = Eg2 - Eg1 ΔEg = -(GMm/r2) -...

I'm trying to express the classical gravitation Einstein-Hilbert lagrangian into some nice way, and I'm having a problem. It is well known that the Einstein-Hilbert action is the following (I don't write the constant in front of the integral, to simplify things) : S_{EH} = \int R \, \sqrt{-g}...

Homework Statement A comet is affected by a gravitational force due to the presence of the Earth. Later, the comet is ten times farther from the Earth. What is the size of the new gravitational force acting on the comet? a) One hundred times larger than before. b) Ten times larger than...

zero gravitation! is it possible 1. Can you tell me the name of two particles having zero force of gravitation between them ?

Just a quick question concerning the concept mentioned in the title to make some clarification. Does an object have to be located at the center of the hollowed out space in a spherical shell (with uniformly distributed mass) for the net gravitational force to be zero? In other words, at the...

Homework Statement The force of gravity on a spacecraft some distance from Earth is 900 N. What will be the force of gravity on a spacecraft with twice the mass, at a distance from Earth’s centre that is as far?

To calculate the exact fall time of a mass, constant g is often used for a short distance traveled as for example in this paper: http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=AJPIAS000044000009000855000001&idtype=cvips&doi=10.1119/1.10277&prog=normal In this paper...

Why physicists are trying to unify gravitation with other 3 forces (weak, strong, e&m)? What if gravitation is actually not a force but a consequence of the mass's disturbance in space-time geometry? (like Einstein proposed) I don't understand their persistence on this unification. Maybe...

Homework Statement If you triple the distance between two objects the gravitational force will... A. Increase by the factor of 3 B. decrease by a factor of 3 C. Decrease by a factor of 6 D. Increase by a factor of 9 E. decrease by a factor of 9 Homework Equations The Attempt...

Homework Statement A student proposes to study the gravitational force by suspending 2 100 kg sperical objects at the lower ends of cables from the ceiling of a tall cathedral and measuring the deflection of the cables from the vertical. The 45 m long cables are attatched to the ceiling 1m...

I didn't put this in any of the physics sections, because I'm only learning this as it pertains to complex analysis. This was just an example provided in a free complex analysis textbook. Basically what I'm asking is why for the law of gravitation, f = GMm/r(t)^2, and it equals the equation in...

I'm trying to rewrite Newton's law - GMP2 = 4(pi)2r3 as P2 = a3 under these conditions: that the mass M is the sun's mass, the radius is 1 AU, and G being converted to the appropriate units. I get stuck on this problem, and I'm hoping you guys are willing to help me out. To begin with, to...

Need help! MTW's Gravitation exercise 16.1! I am working on MTW's Gravitation and I came across a problem. In the attachment https://www.physicsforums.com/attachments/50292, I show my calculation and, finally, I show the contradiction that is, you can get a vanishing \Gamma^k_{\phantom{k}kk}...

what kind of physics should I study to ultimately specialize in general relativity? what fields should i focus on in my B.S and M.S ?

After having read a number of articles about the potential discovery of the Higgs boson at CERN, I am wondering how the "mass effect" generation by the Higgs mechanism can coexist with gravitation as gravitation has been since Newton tightly coupled with the concept of mass. I develop below...

A thought experiment on gravitation... Let us suppose we have a very large planet X which is assumed to have some acceleration 'a'. Suppose we keep on digging a well and afterwards we drop a small mass 'm' then due to the force there will be an acceleration. As acceleration is change in...

This may be a silly question since i am relatively new to the string theory. While going through a quantization of the bosonic string , I see a tower of states appearing corresponding to different modes of excitations of the bosonic string. Now I was trying to figure out how this whole machine...

Homework Statement A planet's mean distance from the sun is 2.00x10^11 m. Determine the planet's orbital period. Use information found in textbook. Homework Equations So I use the following equations: R=h+Rs T=2∏√(R3/GxMs) From the textbook I got the following values...

Gravitation -- Why don't planets smash into each other? Why don't planets smash into each other? The universal law of gravitation states that everything pulls everything else in the universe. Using this logic shouldn't the Sun move because it should be experiencing the pulling force from so...

Homework Statement As the Earth revolves around the sun, if not only travels a certain distance every second, it also causes an imaginary line between the Earth and the sun to pass through a certain area every second. During one complete trip around the sun, the total area would be...

Homework Statement Two bags of apples, each containing 20 apples of equal mass, experience a gravitational force of attraction of 200 units when separated by a distance of 25.0cm. If 10apples are removed from one bag and placed into the other bag, and the two bags are separated by the same...

Homework Statement One of the moons of Jupiter, discovered by Galileo, has an orbital period of 1.44x106s and a mean orbital radius from the centre of Jupiter of about 1.90x109m. From this information, determine the mass of planet Jupiter. Homework Equations I have made a list of...

Homework Statement Determine the speed of a satellite moving in a stable orbit about the Earth if the satellite is 525 km above the Earth's surface. Homework Equations I have made a list of equations that are relevant for this entire module on universal gravitation. So although there are...

Homework Statement Michael has a mass of 75.0 kg and Elaine has a mass of 55.0 kg. If Michael and Elaine are 2.50 m apart from each other as they sit in their Physics class, determine the gravitational force of attraction between them. Homework Equations I have made a list of equations...