Gravitation Definition and 915 Threads

Homework Statement what is the gravitational field strength on the surface of a star that has a radius of 5.0 x 10^6km and a mass of 6.0 x 10^33 kg Homework Equations i tried the F=G MM/r^2 The Attempt at a Solution answer was rly weird and off

The asteroid 243 Ida has a mass of about 4.0×1016 and an average radius of about 16 (it’s not spherical, but you can assume it is). A)Calculate the speed with which you would have to throw a rock to put it into orbit around the asteroid 243 Ida, near the surface. v= ? B)How long would...

Homework Statement NASA is considering solar sailing: using the momentum of light and of massive particles emitted from the sun to help push a spacecraft equipped with large, diaphanous sails. Assume that the density of the material from which the sails are made is about 1000kg.m^{-3}. a)...

Ok so my physics teacher was telling us about the gravitation and he gave us an example of two people standing and he said that these two people are attracting each other. Then he calculated the gravitation force between them. It was a clear thing for me until this. but then he said that they...

Gravitation Potential Energy Problem pls help! I would greatly appreciate help on a couple questions I have. I have been sic for the past few days and unable to go into school to ask my TA's questions. My first question is when should use the equation Ki + Ui = Kf + Uf or Kf -Ki = Uf - Ui ? I...

This is my first topic. I'm sorry for my english: that is not my language. On the planet A, sferically symmetric and with no atmosphere, an astronaut on one pole throws in vertical upwards, a little ball giving to it a certain velocity: this ball reaches the maximum height of 25 cm. The same...

which journal specifically i have to hope a little time for a response of acept or reject? and , where the time of to hope is big?

Question on calculating gravitation per General Relativity and the field equations: I understand that Einstein's field equations describe spacetime. But I’m not sure of how they are used when evaluating gravitation. For example, the equations describe how spacetime is “curved” by a large...

if the paper of gravitation( or other physics ) was submitted to the journal : ¿how long i wait for a response of acceptance or rejeccion? i could sent a publication at various journal simulteneously?

Homework Statement What is the intensity of the force F_{g} between the ring and a mass 'm', which is at a distance 'x' from the center of the ring? http://img52.imageshack.us/img52/6859/ringre.th.jpg Uploaded with ImageShack.us The Attempt at a Solution I have got to my own...

Hi all, I've been reading the Feynman Lectures on Physics and I've stumbled on something. I understand the theory but not how they arrived at the answer. It's to do with firing a bullet from a gun and working out the speed it would need to travel in a curve around the Earth's surface in order...

Okay, so here's my questions: 1. In the theory of the expanding universe, the universe, well, expands. But space it's self would have to expand faster than light could travel or at the same speed for that to work. Umm, Hello? The space would travel faster than light. Would it not? If so...

Can anyone tell me that why we take r square instead of r?

Hey all, I have seen that these two forces combined together have the potential energy of a spring with a constant 'K' as a combination of some sort of the two forces. I have no idea how am I to find this K. All I know Mgh + ρVgh gives the potential energy of a given system let's say. help?

Homework Statement what is the magnitude of Gravitational force for the following picture(s) (attached to forum) Homework Equations Fg = G M*M/D^2 The Attempt at a Solution I tried to do some of them I know the equation for the second one is fG = 2G M*M/D^2 and for the third one...

Hello I have a question. We all know that the center of Earth's gravity is ZERO, as we assume Earth as 100% spherical, We also know that the Earth's mass is not uniformly distributed and its not 100% spherical too. Then how can the Earth's gravity be ZERO at the Earth's center still?

Please teach me this: Why we do not infer the gravity for the force(a type of interaction of fields) but for the distortion of space-time. Thank you very much in advance.

Homework Statement Homework Equations g = GM/r^2 V = (-)GM/r The Attempt at a Solution I know the field strength at the mid point between two masses cancels out but I can't really get my head around the potential. My instinct is telling me that it would also cancel out but I...

is the gravitation source of energy? And yes then can we use this energy with any device?

If an object falls into a black hole, gravitational radiation is emitted. Suppose two identical objects from opposite sides fall into a black hole simultaneously, how do I show that: a. Radiation is emitted. b. Radiation is not emitted.

1) Two planets X and Y (sphere) both have 1 satelite revolving at low altitude about them. If the theri periods of rotation are found to be the same, which of the followings properties regarding X and Y is most likely to the the same? A) Mass B) Average density C) Acceleration due to...

I understand that GR predicts that as an object's speed increases, so does it's mass. I wanted to know if there have been any observations that confirm this, by calculating the gravitational attraction of an object at varying speeds.

High guys, I've always had problems with this law at the way it was explained.But now I've seen lewin explaining that way that bothers me: In terms of sensations.At 1:50 http://youtu.be/M_8w-dD4RBE What I think is that we "feel" the pull only because we are made of multiple particles...

Now there's this paragraph in my physics textbook that just completely went over my head. What does this mean? I could not understand a single word.

I am wondering about that the Earth ( and other planets or suns) have gravitation and magnetic field and that they are working different. I know that the gravitation makes us to stay on the Earth while the magnetic field is protecting us from the sun. another thing i am wondering is that...

Hello, i am so confused Newton's universal gravitation states FG= Gm1m2/r squared and in this case FG stands for the force of gravitational attraction between any 2 objects, but why is Fg (gravitational field strength) equaled to fg=Gm/r squared? why are FG and Fg used interchangeably? i do not...

Homework Statement A 68.5-kg skier rides a 2.56-km ski lift from the base of a mountain to the top. The lift is at an angle of 13.9° to the horizontal. Determine the skier’s gravitational potential energy at the top of the mountain relative to the base of the mountain. Homework Equations Eg=...

Please teach me this: Why we can not resolve the nonrenormalization problem in quantum gravity by freely adding the counterterms with bare parameters nonzero but the corresponding physical parameters being zero. Thank you very much in advanced.

If gravitation is mediated via particle doesn't it mean that this particle would have to escape the black hole to transfer it's gravitation?

1) Graph Fg vs. r Fg on y-axis, r on x-axis (from 1re to 6re) re (radius of the Earth) 2) If a cannon ball is fired from the top of Everest parallel to the Earth's surface fast enough (ignoring air resistance and assuming that it doesn't bump into anything), it will "orbit" the Earth and...

Homework Statement The Attempt at a Solution as w is same as w of Earth ... so T is 24 hrs so its like a geostationary satellite if i use w to find distance ... it comes like 42300 KM if we used t=24 hrs to find distance ... it comes 36000 KM what the hell is this? ... 1...

Homework Statement The Attempt at a Solution Please someone help me to understand the question

Homework Statement Answers: 56. 6.16 x 10^17 N, 57. 894 N Homework Equations Fg = G*m1*m2/r^2 g = G*M/r^2 The Attempt at a Solution 56. Since the closest planet to Z is Y I figured the gravitational force could be calculated by just finding the gravitational force between Z and Y...

Homework Statement Calculate the gravitational potential due to a thin rod of length l and mass M at a distance R from the center of the rod and in a direction perp. to the rod. Homework Equations integral form of Gauss's law wrt gravitation The Attempt at a Solution Can I use...

Assuming a flat, static spacetime, what would the effective force between two objects, with mass m1 and m2 respectively, separated by a distance r from one another, both moving in the same direction with relativistic velocity v, be ?

When (almost any) system emits gravitational waves, does information carried by these waves also 'counted' as an information about a system? In case of BH informational paradox, when BH dissapears, we get not only Hawking radiation, but also information encoded in the gravitational waves of...

What is the Relationship between Kepler's law and universal gravitation law? (IT HAS SOMETHING TO DO WITH THE CENTRE OF MASS)I know this; Newton's Law of Universal Gravitation F=mGM/r^2 derived Keplers Third Law r^3/t^2= constant: mGM/r^2 = mv^2/r gives GM/ (2pi)^2 = r^3/t^2. Read more...

Question on gravitation... Homework Statement A satellite is revolving around a planet in a circular orbit. Its speed is increased from v0 to : (a) (1.5)1/2 v0 (b)2v0 now in the book they have given that in case (a) the orbit becomes illiptical and in case (b) the...

Hi, I'm new here and I hope I'm posting in the right place. I have a question regarding Newton's Law of Gravitation, and it involves the formula: F = GMm/r^2 You know, where F = Force of Gravity, G = 6.67e-11N*m^2, then M and m are two masses, and then r is the distance between the two masses...

Hello, in the equation which describes the force as a function of the radius: F = GMm/R^2 What happens as R approaches zero? or even when R is less than the radius of the planet. mass m will be inside the planet so this formula seems to break down because m will be pulled from both...

1. In an amusement park ride, passengers stand inside an 8 m radius cylinder. Initially, the cylinder rotates with its axis oriented along the vertical. After the cylinder has acquired sufficient speed, it tilts into a vertical plane, that is, the axis tilts into the horizontal, as shown in the...

Circular Motion and Universal Law of Gravitation Homework help! Homework Statement The passengers in a roller coaster car feel twice as heavy as their true weight as the car goes through a dip with a 30 m radius of curvature. What is the car's speed at the bottom of this dip? Given: r =...

Homework Statement 1. A typical white dwarf star, which once was an average star like our Sun but now in the last stage of its evolution, is the size of our Moon but has the mass of our Sun. What is the surface acceleration due to gravity on this star? (Msun = 1.99 x 10^30 kg, Rmoon = 1.74 x...

I'm having trouble with part a) of this question... [PLAIN]http://img69.imageshack.us/img69/5815/98157006.png So I started off by solving the DE above a), and I've gotten it down to: \frac{1}{2} m v^{2} = \frac{mgR^{2}}{(x + R)} + C I can tell I'm getting close, but I'm a little...

[FONT="Comic Sans MS"]*Has General Relativity got some interpretations saying planets and satellites don't act as single mass? *[FONT="Courier New"]Also can it be that orbits of all orbiting bodies are elliptical or seem elliptical due to moving central body?

We just started on a chapter about gravity in my physics class. I'm curious about this: If two rings of different radius and masses of, say, 3 kg and 2 kg, are placed inside each other so that their centers of mass are extremely close (i.e. 1.0 x 10^-9 m) together, would the gravitational force...

Given F is directly proportional to the product of m1 and m2. F is also inversely proportional to the r^2. F, m1, m2 and r are real numbers. Why we can link the above two variations together and say that F=km1m2/r^2, where k is the proportionality constant? Aren't the the variations...

Homework Statement (These are problems I got wrong on a test) 1. How far above the Earth's surface will a person's weight be reduced to half its value at the surface? 2. A 4kg ball and a 2 kg ball are positioned so that their centers are 40 cm apart. With what force do they attract...

Homework Statement The problem is stated here: http://i53.tinypic.com/2wfl4jm.jpg Please take a look.

1. Two spheres having masses M and 2M and radii R and 3R, respectively, are simultaneously released from rest when the distance between their centers is 12R. Assume the two spheres interact only with each other and we wish to find the speeds with which they collide. Write an equation from one of...