Gravitation Definition and 918 Threads

I know it is 9.8 m/s^2. However, we're covering Kinematics, and I'm just wondering how you know whether you use -9.8 or +9.8. At first, I thought that if the object was traveling up, you would use +9.8 and if it was going down, you would use -9.8. But I just went over a problem that used +9.8...

hello all i was wondering if we could use Newton's F=GMn/r^2 to apply it to non-point masses, and specifically, if they two masses come completely within each other, would it still hold?

guys i need help with these problems.I have been trying to solve then for a long time and still cannot as i am very confused and have no where to go for help 1) On the way to the Moon , Apollo astronauts passed a point after which the moon's gravitational pull became stronger than the...

I was wondering if someone could tell me if I did this right: Two neutron stars are separated by a distance of 10^10m. They each have a mass of 10^30kg and a radius of 10^5m. They are initially at rest relative to each other. How fast are they moving when they collide? R = 2r + d =...

Hi, i surely do appreciate some help here.. How is gravity on the Earth surface related to the circular motion of the Earth about its axis? If I'm not wrong, my lecturer once taught me that i can actually equate both gravitational force and centripetal force together since they are both...

Newton's Law of Gravitation Derivative Hi, I was wondering if anyone could help me find the derivative of Newton's Law of gravitation [F=(GmM)/r^2] and what it means? What does the minus sign indicate? I'm kind of confused on the subject at hand and hopefully someone can help out. Thanks

i was doing some reading on Newton's law of universal gravitation. the equation is given as mass of 2 objects divided by distances square and then multiply by gravitation constant. using 50kg and 100 kg mass and a distance of 2 metres i get a value 8.34e-8 N this a small force, which sets me...

Sir, A body is projected in space from the earth’s surface with escape velocity. It is said that at the time of projection its total energy is Kinetic. Is it true? If so, doesn’t it have gravitational P.E at the time of projection?

i wonder, the book by kip thorne and john wheeler called gravitation, is it a technical textbook on gr? and on a scale of 1-5 (1-easy 5 extremely hard) how would you rate this book? are there any other challenging textbooks on GR?

Please help me prove - A uniform spherical shell mass is cut into two pieces parallel to one of Symmetry axis. Prove that the gravitational field intensity due to the mass at the centre of the cross sectional plane parrallel to the symmetry axis is same for both the parts.

The situation involves a neutron in a constant gravitational field (g=9.8). I need to find the energies of photons that transition to the excited state. I solved the Schrodinger equation by doing a variable transformation using Airy functions. To fully solve, however, I need to find the roots...

I can't seem to figure this one out. A particle at rest is attracted to a center of force by the relation F=-mk^2/x^3 what is the time it takes for the particle to get to the force center from a distance d in terms of d and k? I can't seem to find any equations that will help me out on...

Hi all, I'm going to spend my summer doing some self-study in the subjects which I'll be covering in the future and I think it'd be a great time to dive into relativity. I've had some education in special relativity but I've never dealt with general relativity. I'd like a good, thorough...

Hey guys, I have a few Circular Motion and Gravitation questions that I have almost no idea how to do: 1. The orbital radius of Mars around the Sun is 1.52 times that of Earth's orbital radius (1.50 X 10^11m). In Earth years, what is the period of revolution for Mars in this orbit? (I need to...

The radius Rhand mass Mh of a black hole are related by Rh = 2GMh/c^2, where c is the speed of light. Assume that the gravitational acceleration agof an object at a distance Ro = 1.001Rh from the center of a black hole is given by Ag = G M / r^2 (it is, for large black holes). (a) What is ag at...

Hello all, I was wondering if someone could please help me with a problem. It is regarding the law of universal gravitation, this time using conservation of mechanical energy. We know that F = GMm/R^2 **If a projectile is launched from Earth with a speed equal to the escape speed, how...

A projectile is shot straight up from the Earth's surface at a speed of 6000 km/hr.How high does it go? i started out by converting km/hr to m/s so i got 6000km/hr= 1666.666666m/s then i used this formula: v^2=2gy and i got: y= 141723 m= 141.723km (i just got lucky that my answer...

Let's discuss the Dirac equation in a gravitation field. I suggest to begin with the following article: http://arxiv.org/abs/math.DG/0603367" It is rather simple. Your comments would be helpful for me.

Q:Suppose that a binary star system consists of two stars of equal mass. They are observed to be separated by 340 million kilometers and take 5.0 Earth years to orbit about a point midway between them. What is the mass of each?

Q:Two objects attract each other gravitationally with a force of 3.3 10-10 N when they are 0.25 m apart. Their total mass is 4.0 kg. Find their individual masses. Now my professor only told us to use F= Gm1m2/r2 Force in this case would be the 3.3e-10 Newtons, the radius squared = 0.0625 m...

I'm having an argument with a co-worker about gravitation and need some "enlightened" advice. The argument is whether or not two objects dropped at the same time would impact the surface at EXACTLY the same time or not. I already presented the proof that when combining the law of...

In Figure 13-34, a square of edge length 22.0 cm is formed by four spheres of masses m1 = 7.00 g, m2 = 3.50 g, m3 = 1.50 g, and m4 = 7.00 g. In unit-vector notation, what is the net gravitational force from them on a central sphere with mass m5 = 2.30 g? Okay this is what I did so far...

Satellite A has a mass of 1000kg. Satellite B has a mass of 2000kg. BOth are in orbit 250km above the surface of the earth. Satellite A will have an orbital speed that is ____ satellite B. 1. the same as. 2. four times that of. 3. twice that of. Not really sure on this. I originally said...

Hello, please Can I have some guidance for the problem: The heigth achieved in a jump is determined by the initial vertical velocity that a jumper is able to achieve. Assuming that this is a fixed number, how high can an athlete jump on Mars if she can clear 1.85m on earth? Thank you B

Hi I am stuck with this problem: A deep hole in Earth reaches a depth of one half of Earth's radius. How much work is done when a 1-kg mass is slowly lifted from the bottom of the hole to Earth's surface? I use the expression of the gravitation force, F=GMm/R3 so the work would be: integral...

1.) Consider attached image (P13.41). Determine the escape speed for a rocket on the far side of Ganymede. The escape speed from Ganymede without Jupiters influence would be \sqrt{\frac{2GM_{gan.}}{r_{gan.}}}. Now the ship will have a velocity equal to that of the escape velocity needed to...

Can anyone help me with this problem? Approximate the gravitational force of attraction between a 46.0 kg girl and a 52.0 kg boy if they are sitting 3.0 m apart in physics class. Since the formula is [(m1m2/r^2)]G=Fg. So I first tried [(46+52)/3^2]6.67e-11 and I got 7.27e-10. Then when...

here's the question (from mastering physics): "The weight of a person at the equator, as determined by a spring balance, is 750 N. By how much does this differ from the true force of gravitational attraction at the same point? Assume that the Earth is spherically symmetric." Now, i would...

The center-to-center distance between Earth and Moon is 384400 km. The Moon completes an orbit in 27.3 days. (b) If gravity were switched off, the Moon would move along a straight line tangent to its orbit, as described by Newton's first law. In its actual orbit in 1.00 s, how far does the Moon...

Hi, all. I have a problem I wish to solve. It's not from a textbook, I thought of it myself. If two masses of 1 kilogram each are 1 metre apart in space, how long will it take for them to reach each other from their attractive gravitational forces? Remember that the force (and hence the...

How would our universe have evolved without gravitation, and how so would the universe appear at present? Does such a situation somehow differentiate the possible perspectives of spacetime with or without compactified dimensions?

Hi, how does one go about finding the aphelion distance when all the information you've got is the satellite's velocity at one point in time?? Here's the Q: 1) first you're to find an expression for the velocity of a satellite in circular orbit about planet of mass M. The orbit radius = r...

On dealing with Universal Gravitation topic, I came across this question: what is the min speed, relative to the sun, necessary for a spacecraft to escape the solar system if it starts at the Earth's orbit? My working: v=sqrt(2GM/R), where G=universal constant, R= distance between Earth...

There's an inclined plane with theta unknown. The frictional coefficient is 0. m1 is higher on the inclined plane than m2. m1 = 1680kg m2 = 152kg Distance between the two: 11mm At what angle of inclination will the 2nd mass begin to slide down the plane? Normally (without 2 objects)...

I know they involve F= G(m1 x m2)/r^2 1) Two objects attract one another gravitationally, with a force of 2.5 x 10^-10 N when they are .25 m apart. Their total mass is 4.0 kg. Find the individual masses.

Hi i was wondering if anyone could help me with the following problems please,I'm a bit confused! Q1. A 9.4 kg projectile is fired vertically upwards. Air drag dissipates 68 kJ during its ascent. How much higher would it have gone were air drag negligible? Here I used the formula mgh and...

1) if something is 5 Earth radii above the Earth's surface and you know its mass, how would you figure out force of gravity on it? 2)and given the radius and mass of a planet how would you be able to figure out the acceleration due to gravity on it?

Here's the problem I've been working on. Gold has density of 19.3x103 kg/m3. How big would a solid gold sphere have to be if the acceleration due to gravity at its surface is to be 9.87 m/s2? (Check your answer against the radius of the Earth, which has a mean density of 5.5x103 kg/m3.)...

Will anybody let me know what is the relation between the moon's gravitation and the level of ocean in earth?As far I know that during newmoon and full moon day the level of ocean increases.

At what height above the Earth's surface would an object's weight be one half the value at the surface? W = m(2)g = Gm(1)(m2) / r^2 is the formula I am using. I found 1/2 weight to be 2.92825 x 10^25 Then I found m(1) to be 1/2gxW (not sure if I should've used 1/2g here or not) and then...

Firstly, I admit that my math skills are fairly rusty. I also admit that this is a homework problem. It is not to be turned in for a grade however. The problem is to determine the SI units of G in the following equation: F = GMm/r^2 (where F is force (mass *...

Just a question from a begginer : In the simulation of a solar or (galactic) system, when you calculate the position of a planet P at time t+dt, you only know the position of the other bodies in the system at time t, so you calculate the distance d between P and any other body Q at time t...

I don't understand why the physics book defines the centripetal force and gravitational force acting in different directions. N - m*(acceleration of gravity) = -m*r*w^2 N = m*(acceleration of gravity) - m*r*w^2 Why don't the acceleration of...

:confused: Hello I need some help understanding Newtons universal gravitation. I read on a site that an objects Force on Earth is its mass x gravity(on earth) hence MG (like F=MA). Then they say using Newtons inverse square law that the same object at a distance of the moon would have the...

About a week back I posted in the strings forum asking about how current theories interpret gravitation and how they differ from general relativity. But the main subject of the thread wasn't how physical theories should be interpreted, so I'd like to pose that question again, in greater detail...

i am inquiring of just what the topic suggests... anything that anybody knows about gravitation...theories, equations, its relations to qm and anything else...post if you know something about this subject other than that it makes stuff attract to each other.

this seems like a foolish question to myself, though i have never though to ask it, and decide to do so now on the off chance it has any relevancy. how would waves of gravitation affect particulate matter, would it cause this matter to bahave in a wave like manner as gravity does itself?

Hey there! Completely new here but thought someone could help. I have this problem where I don't even know where to start from. The problem: (Picture of loop with a man in a roller coaster cart hanging upside down from furthest top point of circle) A man in the roller coaster is...

Does anyone know the proof for Newton's law of gravity, because i looked in a lot of books for this proof but i didn't find it anywhere! Slowly I'm getting a little cautious about what we're easily accepting in school! Thanks for your reply.

Hello I'm a beginner in physics and came across an explanation for Gravitation, it explains it using the moons orbit around Earth as an example, they also say firing a projectile at a certain velocity can put that projectile in orbit, but they confused me with that one, can anyone help? this is...