Gravitation Definition and 918 Threads

For question A, I know that I am supposed to input the numbers given into the Universal Gravitation Equation, but I do not know how to solve for it beyond that. For question B, I know that the astronauts weight depends on the mass and gravity of the new planet but I do not know how to prove it...

Using Kepler's Formula, I tried to solve for the answer but was told that it's incorrect.

I was recently working on the two body problem and what I can say about solutions without solving the differential equation. There I came across a problem: Lets consider the Kepler problem (the two body problem with potential ~1/r^2). If I use lagrangian mechanics, I get two differential...

So my doubt is at the beginning of the problems hey are saying that the ball obeys stokes law and on the latter part of the question they are saying that no buoyant force is acting then how does the velocity of the ball change in the end? Also what is the use of specifying 'the ball never...

So I already have a solution available to this problem and the link for the solution is: I have understood everything in the video except the part where they are equating the force dF=GM/r²*dm According to my reasoning the inner part of the sphere (the part below the dm element we have taken)...

suppose suddenly the sun disappears at a time t. at this arbitrary time t, the Earth should fling off tangentially to the point in its orbit at time t as there is no centripetal force keeping it in orbit. we know light takes about 8 minutes to reach the earth. so will humans on Earth experience...

The value of acceleration due to gravity at a depth 'd' inside the Earth is given by- g' = g(1 - d/R) which can also be written as g' = g(x/R) from the diagram so that x'' = (w2)x where w2 = g/R is the angular frequency Hence the time period T is given by T = 2π sqrt(R/g) but the question...

Express the condition of 𝜎 where the celestial body B collides against the celestial body ASo this is the original figure of the problem. This is my attempt at a solution Since I need to find σ, I have assumed sigma to be an multiple of the radius ## R ##. So, let ## \sigma = \lambda R ##...

I figured out stokes law equation but I am unable to proceed further

I can say that the frictional force always against the rolling sphere and the velocity is increasing for the ball. So The dot product F.v keeps on getting more and more negative, so how can the Pf remain constant? Well the velocity increases along the incline and the force of gravity is down...

I do not know how to do this because in order to find the force of gravity it seemed to me i need to know the mass of the planet and vice versa, and for the 1st exercice i do not know whether the planet fills the astronaut's field of view. If it does in understand that i need to use trigonometry...

Hi, starting from this very interesting thread I'm still a bit confused about the conclusions. The main point, as far as I can understand, is all about conditions for a quadrilateral to be considered a parallelogram. My first basic doubt is: the concept of 'parallel' applies just to geodesic...

Does someone know of an official or unofficial errata for the above book of Weinberg?

Hello, and thank you again to anyone who can confirm if I have the right answer or who can give me some suggestions. This question felt like a bit of a surprise because we have not yet covered one where the mass of a planet was missing. Thus, my confidence in my work is low. Part b felt like a...

Homework Statement: Henry Cavendish succeeded in measuring the value of the constant "G" way back in the late 1700s. His method was to put two known masses at a known distance and measure the attractive force between them; then he could use Newton's Law of Universal Gravitation to find "G"...

I tried to solve for mass of the mountain by: (mass of ball) (9.8m/s^2)= G(mass of ball)(mass of mountain)/ (15000m)^2 The mass of the ball cancels out leaving with mass of mountain=33.04 * 10^(18) kg.

Homework Statement: The particle is moving in circular orbit such a way that the net force (F) is always towards the point p (point p is on the circumference of circle). Find the variation of force F with respect to r. i.e find the value of n in the expression F=kr^n Homework Equations: F=kr^n...

Nieuwenhuizen uses a method for calculating the propagator by decomposing the field ## h_{\mu\nu}, ## first into symmetric part ## \varphi_{\mu\nu} ## and antisymmetric part ## \psi_{\mu\nu} ##, and then by a spin decomposition using projector operators. Using this he writes the dynamical...

I didn't use Kepler's 3rd law and this may be the reason I have a wrong answer. However, I want to know: where I make the mistake. ## ma = \frac {G M m} {R^2}## ## R = (\frac {G M} a)^{1/2}## ##a = \frac {v^2} R## ##V^2 = a R = a (\frac {G M} a)^{1/2} = (G a M)^{1/2}## ##V = (G a M)^{1/4}##...

Okay, so let's simplify things and look at the ideal case, where the 2 masses are the same. Well, this gives us a sine wave pattern to the orbital velocity. Consequently, the acceleration would follow a cosine wave since the derivative of velocity is acceleration and the derivative of sine is...

Why air resistance has less force than gravitation force in free fall? If Egg is fall from a nest of tree, while falling, it has less magnitude of air resistance than gravitation force. Where net force is not equal to zero.

First, I started with F_a = m_aa_a=G \frac{m_am_b}{r^2} and F_b = m_ba_b=G \frac{m_am_b}{r^2} . Solving for their respective accelerations, I got a_a=G \frac{m_b}{r^2} = 100G and a_b=G \frac{m_a}{r^2} = 100G, meaning that the initial acceleration of the two point particles are each 100G ...

Why do we use the equation ##\frac {1}{2}mv^2 = \frac {GmM}{r}## to derive potential velocity, and then put that in the Lorentz factor in order to derive gravitational time dilation? Shouldn't we be using the relativistic definition of kinetic energy -> ##mc^2(\gamma - 1)## to derive the...

im confused about this thing, because they said Earth's acceleration due to gravity is independent from the mass of the thing dropped

Homework Statement In the far future, humans have built a space elevator as a cheap means of access to space. However before that could be done, a few basic principles had to be worked out. . . a) What is the minimum initial speed (in an Earth-centered inertial reference frame) needed for an...

Homework Statement There is an infnite high hydrostatic head in an infite high tank on the surface of earth. How big is the pressure p(r) in tank at a distance r. Ignore the rotation of the Earth and assume the water stays liquid. ( So basically ignore it's an impossible scenario )...

Homework Statement Given in the picture attached below[/B]Homework Equations ? The Attempt at a Solution I had no idea how to tackle this problem.[/B]

How can it be easily shown that it's a bad idea to develop relativistic gravitational theory in full analogy with electromagnetism? I.e. why not to introduce 4-potential for gravitation in analogy with 4-potential in covariant form of Maxwell equations and get something fully analogous to...

since it is known that ##\vec{A_\perp} = -{mG \over R^2}## why did the professor write it as ##\vec{A_\perp} = {- R G \rho \over 3}## for perfect sphere with perfect mass distribution ? Shouldn't it be ##\vec{A_\perp} = -{4 \over 3} \pi R G \rho##? I need help thanks.

<Moderator's note: Several threads merged and moved to cosmology.> So I’m wondering about gravity. I was under the impression that gravity was created due to the curvature of 4d spacetime and whatnot. Can someone explain to me what gravitons are in relation to that? Are the gravitons making...

I have been googling this topic for some time, but I still don't know if this is still an unsolved mystery of physics (it's just so) or if there is a deeper underlying theory. I get the idea that mass/energy distorts spacetime, justified by thought experiments with moving objects and photons...

I recently watched a video on youtube where a guy fires a 50 cal. rifle straight up into the air and measures the time of flight at about 100s. It got me thinking about what altitude the round reached. So I used the kinematics equations and obtained a value of 12.25km. Amazing, but I wondered...

I have been going through problems in my textbook and have a question. The chapter is on gravitation and orbital mechanics. When answering the problems I seem to head towards different methods than what the book prescribes. My answers, primarily using known orbital equations, are close, but not...

Homework Statement The distance between the centres of the Earth and the moon is 60 times the radius of the earth. Calculate the centripetal acceleration of the moon. Acceleration due to gravity on the Earth's surface is 10m/s. Homework Equations Centripetal acceleration= v^2/R Orbital...

Can someone please show that calculation of gravitational potential energy at a point R+h from the centre of the Earth by choosing the centre of the Earth to be at zero potential. Here R is the radius of the Earth and h is not very small wrt to R

okay, so I’ve had this random thought. We have all been told that objects fall to the ground at the same speed, even if they have different masses. While it’s true that any two objects, regardless of mass, will accelerate towards Earth at the same speed, that doesn’t mean the Earth is...

Homework Statement Homework EquationsThe Attempt at a Solution I think if the law of gravitation changes then the law of areas should still hold .Law of areas is nothing but law of conservation of angular momentum . Since the changed law of gravitation is still central the law of areas...

Homework Statement Homework Equations f = ma m1 = mass of moon m2 = mass of earth The Attempt at a Solution Ok this is crunch time here and i am NOT Kobe Bryant I have chosen gravitation between the moon and Earth for this project. I will start with the net force on the moon as ∑FSystem =...

Homework Statement I'm working on a generalization of gravitation to n dimensions. I'm trying to compute gravitational attraction experienced by a point mass y due to a uniform mass distribution throughout a ball of radius a -- B(0, a). Homework Equations 3. The Attempt at a Solution [/B]...

can two planets share the same orbit

For all the theorists on gravitation, I would beg to ask a question on mass and it's proportional effect with gravity. IE :Greatest mass = Heaviest object. Simplistically, Why do objects with the highest mass become attracted to the nearest highest mass? Bowling ball falls to Earth via...

Homework Statement Hi I'm attempting to derive the gravitational potential energy of a point mass (##m##) that's moving from infinity to a point r' inside a gravitational field produced by a another mass ##M##. For simplicity I treated it as a one dimensional case. The problem I get is that the...

Homework Statement A binary stellar system is made of one star with ##M_1=15{M}_\odot## and a second star with ##M_2=10{M}_\odot## revolving around circular orbits at a relative distance of ##d=0.001pc##. At some point ##M_1## explodes in a supernovae leaving a neutron star of mass...

Homework Statement We have a crate sitting on a scale that is on the surface of the Earth. We want to come up with the value of the acceleration due to gravity, ## g ##, when we take into consideration the rotation of the Earth. Homework Equations In the book, here's how they go about this...

How is the centrifugal force in an orbiting planet or star, balanced if according to Einstein there is not such gravity force and is only space time curvature. Also, how come in order to determine internal pressure of a planet or star, the force acting near the center is calculated using the...

Homework Statement ##\alpha##-Centuary is in a binary visual system with another star. Their separation, from their CM, is 8.0'' and 9.7''. The distance from the Earth is 1.31pc. Their revolution period around the CM is 80.1 years. I have to find masses and luminosities for each star. Homework...

1Problem: Two equal satellite, A and B, of a planet of mass M, describe circular trajectories where the radious are 0,5r and r. We can afirm that: A- The intensity of gravitical force acting on B is half of the gravitical force acting on A; B- The value of centripetal aceleration of A is one...

Homework Statement What is the distance from the Earth's center to a point outside the Earth where the gravitational acceleration duo to Earth is 1/10 of its value at the Earth's surface? Homework Equations F = Gm1m2/r2 F = m1 (v2/r) Mass of Earth = 5.98x1024 G = 6.67x10-11 The Attempt at a...

Homework Statement You are on a deep space mission to search for Earth-like planets. Your crew locates a possible planet and with scanners finds the radius to be 7.5 x 106 m. A team lands on the surface. There, they hang a 1.0 kg mass from a spring scale. It reads 8.5 N. Determine the mass of...