Gravitation Definition and 918 Threads

Homework Statement A landing craft with mass 1.22×10^4 kg is in a circular orbit a distance 5.50×10^5 m above the surface of a planet. The period of the orbit is 5100 s . The astronauts in the lander measure the diameter of the planet to be 9.50×10^6 m . The lander sets down at the north pole...

Hi PF I am reading Feynman's lectures on gravitation. The equivalence principle says that no local measurement (it includes measurement of the electromagnetic field) can tell you if you are accelerated or in gravity. Feynman agrees and writes that we have then a problem. Accelerated charges are...

Homework Statement ANY HELP IS WELCOMED[/B] The single moon of an Earth-like planet creates tides on the planet that are slowing the planet’s rotation. The planet’s rate of rotation is decreasing at a rate of 7.00 x 10-7 radians/sec/century. The mass of the planet is 6 x 1024 kg, and its...

I was just wondering, what if an object is placed in our solar system, will it revolve around the sun? If yes, will it have a centripetal acceleration too?

Millikan Oil drop experiment. For my current lab, we are recreating the milian oil drop experiment to measure the charge of an electron. However, we are using 1-micron diameter latex spheres in place of oil drops. Problem: I am having difficulty deriving an equation for the speed of the drop...

Pressure can exist in a container of gas even if there is no gravity. From kinetic theory of gases it is assumed that pressure exists due to momentum transfer between molecules and the wall. Suppose I have a closed container on Earth at sea level filled with air. Now I carried it to zero gravity...

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...

In relation to two objects with a gravitational field on them (i.e. a planet and its moon), would there be two pairs of partner forces (the force of gravity exerted from each object and the resulting partner force from each force of gravity)? For example with the Earth and moon: 1. Force of...

I've just reached the opening in chapter 2 wherein there's a brief discussion of concepts and math which should be familiar to the reader (Basic SR stuff it seems), and I'm not familiar with it unfortunately. I am familiar with future and past light cones, and the language of causality, but not...

Hey there, I have two questions - the first is about an approximation of a central gravitational force on a particle (of small mass) based on special relativity, and the second is about the legitimacy of a Lagrangian I'm using to calculate the motion of a particle in the Schwarzschild metric...

Homework Statement If the gravitational accleration at the Earths surface is 9.81 m/s^2 what is its value at a height equal to the diameter of the Earth from its surface? 2. The attempt at a solution I have heard that it becomes 1/4th the value as the center of mass is moving away form each...

Homework Statement If we take the gravitational acceleration at the Earth's surface as 10,/s^2 and the radius of the Earth as 6400km, decrease in the value of the gravitational acceleration g at a depth of 64 km from its surface would be ...,/s^2 2. The attempt at a solution I was never really...

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...

Homework Statement If a curve with a radius of 88m is perfectly banked for a car traveling at 75km/h, what must be the coefficient of static friction for a car not to skid when traveling at 95 km/hr 75km/h = 20.8m/s 95km/h = 26.4m/s Homework Equations Fr=mv^2/r Fr=centripetal force m = mass r...

Homework Statement The question is attached Homework Equations Kepler's laws and gravitational equations The Attempt at a Solution the question gave me a and T, I related it with Kepler's third law a^3/T^2, then I don't know what to do next. The answer of part a is 1.27 x10^17 /r^2 , part b =...

Hello, I would like to ask, if somebody knows anything about comparison post-Newtonian approximation of gravitational waves and these which were detected. Or generally post-Newtonian predictions vs. facts found in detection. I tried find some article but I didn't find. Please let me know what...

I have found an article about an experiment that states that gravity on a small scale doesn't experience quantum effects. Of course the headline has been catchy, so I want to ask about the real importance or relevance of the experiment. Or for short: Do the results imply any consequences on...

Homework Statement Two bodies A and B having masses m and 2m respectively kept at a distance of d apart. A small particle is kept between A and B such that the net gravitational force on the particle is zero due to the bodies A and B . Its distance from mass A should be ? Homework...

I was looking for this book but it appear that is out of print and the only copies available are very expansive, so what book would you recommend on GR? I mean, i want some in-depth textbook. Thanks! ;)

Homework Statement A solid cylinder of uniform density of 0.85 g/cm3 floats in a glass of water tinted light blue by food coloring. https://s1.lite.msu.edu/res/msu/kashy/physicsLib02/32_Fluids1_Pascal_Arch/graphics/archimedes.gif Its circular surfaces are horizontal. What effect will the...

Homework Statement A small solid sphere of mass M0, of radius R0, and of uniform density ρ0 is placed in a large bowl containing water. It floats and the level of the water in the dish is L. Given the information below, determine the possible effects on the water level L, (R-Rises, F-Falls...

Homework Statement Homework Equations $$\frac{\omega}{v}=\frac{s}{r}$$ The Attempt at a Solution How to get the equation above? Cause $$\frac{s}{r}=\omega$$ & $$\frac{\omega}{v}=\frac{1}{r}$$ since v=rw. Source: http://www.relativitycalculator.com/Newton_Universal_Gravity_Law.shtml

Hello. Modern Physics explains Gravitation in two general ways: In accordance to the General Theory of Relativity, Gravitation is thought of as an effect of the curvature of space-time continuum. This results in the formation of the recently and famously detected Gravitational Waves. Quantum...

Homework Statement [/B] Two 100-kg thrill seekers are diving into a neutron star. The neutron star’s mass is 1.1 solar masses and its radius is 12.0 km. For safety, they tie themselves together with a cord 10m long, so that as Melvin reaches the surface of the neutron star, Fred is 10.0 m...

I am asked to find the total gravitational energy of a hollow sphere using the fact that the field energy density is given by ##u_g = \frac{-1}{8\pi G}g^2##. Now, ##g = \frac{Gm}{r^2}## in this case and substituting gives ##u_g = \frac{-GM^2}{8 \pi r^4}##. Integrating this over volume will give...

Homework Statement The elliptical orbit of a comet is shown above (hidden document I apologize but easy to picture). Positions 1 and 2 are, respectively, the farthest and nearest positions to the Sun, and at position 1 the distance from the comet to the Sun is 10 times that at position 2. What...

On applying definite integral to find work done, we integrate F.dx and apply lower and upper limits. Should we apply the dot product, before integration , that is -1 for θ = 180, 1 for θ = 0. Or will the limits applied and their values suffice in deciding the sign of the final value. I have...

This is a somewhat weird question, but here it goes: What would happen if there were only gravitons? Would some other kind of particle appear in the Universe sooner or later? Would there be any chance for mass to appear in such a Universe (assuming that the graviton is a massless particle)...

Homework Statement Show that the rate of change of the free-fall acceleration with vertical position near the Earth's surface is \frac{d}{dr} [g] = -\frac{2GM_E}{R_E^3} Assuming h is small in comparison to the radius of the Earth, show that the difference in free-fall acceleration between...

I'm studying effective potential in Newtonian gravitation. The mechanical energy of a body can be written $$E=\frac{1}{2}\mu {\dot{r}}^2+\frac{L^2}{2\mu r^2}-\gamma \frac{m M}{r^2} \tag{1}$$ Where \mu is the reduced mass of the system planet-star. Consider now the term...

I'm studing Gauss law for gravitational field flux for a mass that has spherical symmetry. Maybe it is an obvious question but what are exactly the propreties of a spherical simmetric body? Firstly does this imply that the body in question must be a sphere? Secondly is it correct to...

Take an object of negligible mass that is dropped from rest 2 kilometers away from a neutron star of mass 1.989*10^30 kilograms (1 solar mass) and radius 7,802 meters. How long will it take the object to reach the surface of the neutron star? I'm not terrible at calculus, but I know for a fact...

Homework Statement Are 11,2km/s enough, to wrest away from the Suns gravitational field? (We are departing away from the Earth planet, away from the sun) Here I am unsure if I should use Suns Radius or Earths Radius r. I think that Suns Radius would be more logical, since the problem is about...

Homework Statement This problem only requires to find h, but I want to make sure that I also found Me and g correctly. Starting with Newton's Law of Gravitation, determine the height h one person has to go from the surface of the Earth in order for that person's weight to be reduced to...

Hi everyone, When I graduated college about 4 years ago I had to, regrettably, sell off many of my math/physics books to pay back my student loans. One of my favorites was Gravitation. For the past few months I have been looking to buy it again, but it looks like all of the major sellers...

Four 9.5 kg spheres are located at the corners of a square of side .60 m. Calculate the magnitude and direction of the total gravitational force exerted on one sphere by the other three. So, essentially my question is, why can I not use center of mass of the other 3 spheres to calculate the...

Homework Statement [A rocket has landed on Planet X, which has half the radius of Earth. An astronaut onboard the rocket weighs twice as much on Planet X as on Earth. If the escape velocity for the rocket taking off from Earth is v , then its escape velocity on Planet X is a) 2 v b) (√2)v c) v...

Homework Statement The picture has the problem question. OK. When the moon is at point B, the distance from the moon to the center of the planet is most nearly: A) (1/25) * rA B) (1/5) * rA C) (1/ sqrt(5) ) * rA D) rA E) sqrt(5) * rA. Homework Equations Newton's law of gravitation...

Does the fact that orbital electrons are stable suggest that gravitation is quantized, analagous to the observation that the stability of orbital electrons suggested that electromagnetic energy was quantized?

Homework Statement The value of g at a point P inside the Earth and at another point Q outside the Earth is g/2. Maximum possible distance in terms of radius of Earth between P and Q is? (g being the acceleration due to gravity on the surface). Homework Equations gh = (1+h/r)-2g...

Hello. I have 2 books in General Relativity: MTW Gravitation and Bernard Schutz First Course in General Relativity. I studied Calculus I, II, and have a basic understanding of Linear Algebra(did not studied extensively). I want to learn about GR as much as possible, and improve myself to become...

Homework Statement I want to know how this equation is getting solved to r. I know the result, but I want to know how :) Homework Equations γ*m*Me/r = 4Π2*m*r/T^2Solution does need to be: r = ^3√γMeT^2/4Π^2 (^3√ should mean the 3rd root/radical) The Attempt at a Solution I am so far...

What is the trace of a second rank tensor covariant in both indices? For a tensor covariant in one index and contravariant in another ##T^i_j##, the trace is ##T^k_k## but what is the trace for ##T_{ij}## because ##T_{kk}## is not even a tensor?

Hi! I am currently trying to write a code in C to simulate the orbit of planets around the Sun in the solar system. I am using the velocity Verlet approach and finding that my code produces no acceleration in the ##y##-direction (aside from for ##t_n = 0##,) and that the planet just flies off...

A given planet has a mass, M = 6.42*10^23 kg, and radius, R = 3.39 * 10^6 m. The gravitational konstant is G = 6.67*10^-11 A spaceship with mass m = 4000 kg is launched from the planets surface. How much energy is needed to send the spaceship to a height h = 100 km above the planets surface?

Help! Has anybody made a case as to why the inverse square law should apply to gravitation, a case that is based on pure reasoning, instead of empirical evidence? I have been trying to find such arguments, but no luck so far. Janein

So, i was on the plane going for oxford interviews and i was thinking about what i could be asked. While i was thinking i came up with this one. Suppose the Earth and the moon were at a distance α apart at rest, how long would it take for them to crash into each other. I'm only really...

Coulombs law states 2 point charges of opposite sign will attract where acting simultaneously on two point charges and as follows: The formula calculates the force that will act and implies the force be equally experienced by both points of charge even if one charge is much greater than...