What is Gravity force: Definition and 30 Discussions

Gravity (from Latin gravitas 'weight'), or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are attracted to (or gravitate toward) one another. On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides. The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing and forming stars and caused the stars to group together into galaxies, so gravity is responsible for many of the large-scale structures in the Universe. Gravity has an infinite range, although its effects become weaker as objects get further away.
Gravity is most accurately described by the general theory of relativity (proposed by Albert Einstein in 1915), which describes gravity not as a force, but as a consequence of masses moving along geodesic lines in a curved spacetime caused by the uneven distribution of mass. The most extreme example of this curvature of spacetime is a black hole, from which nothing—not even light—can escape once past the black hole's event horizon. However, for most applications, gravity is well approximated by Newton's law of universal gravitation, which describes gravity as a force causing any two bodies to be attracted toward each other, with magnitude proportional to the product of their masses and inversely proportional to the square of the distance between them.
Gravity is the weakest of the four fundamental interactions of physics, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a consequence, it has no significant influence at the level of subatomic particles. In contrast, it is the dominant interaction at the macroscopic scale, and is the cause of the formation, shape and trajectory (orbit) of astronomical bodies.
Current models of particle physics imply that the earliest instance of gravity in the Universe, possibly in the form of quantum gravity, supergravity or a gravitational singularity, along with ordinary space and time, developed during the Planck epoch (up to 10−43 seconds after the birth of the Universe), possibly from a primeval state, such as a false vacuum, quantum vacuum or virtual particle, in a currently unknown manner. Attempts to develop a theory of gravity consistent with quantum mechanics, a quantum gravity theory, which would allow gravity to be united in a common mathematical framework (a theory of everything) with the other three fundamental interactions of physics, are a current area of research.

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  1. J

    Electron bound to proton by gravity

    Hello everyone, I have the problem above. I chose to put ##F_G = F_Z## to solve it and end up with a radius ##r = 1.04\cdot 10^{-7}##m. Solutions on the internet choose to put the gravitational force equal to the centrifugal force and obviously end up with a completely different solution. I...
  2. Lotto

    What minimum speed do we need to give a charged ball?

    First, if we sign the speed in the highest point of the ball's trajectory to be ##v_2##, we can write ##m\frac {{v_2}^2 }{l}=T_2+mg-\frac{1}{4\pi \epsilon}\frac{Q^2}{l^2}##. Now, depending on the ball's particular mass, the electrostatic force can be bigger of smaller than its gravity force...
  3. Lotto

    What is density of dark matter as a function of distance from the galactic core?

    This problem builds on my previous post, where we calculated that core's mass is ##M_1=\frac{{v_0}^2r_1}{G}##. So if we consider mass of dark matter dependent on distance ##r## to be ##M_2(r)##, we can calculated it from ##G\frac{(M_2(r)+M_1)m}{r^2}=m\frac{{v_0}^2}{r}.## So...
  4. Cassis

    B Circular wire center of gravity

    The center of gravity of a circular wire should be in its center? What would happens if we put a marble and a wire into an empty space. Would the gravity force skyrocket as the marble approach the wire center of gravity?
  5. NeedFreedom

    I Gravity machine force calculations assistance needed

    Im prototyping a machine to lower liquid from a height using a chains and sprockets. Essentially liquid will fill at top, be lowered over a distance of 4.8 metres then emptied at bottom. The liquid needs to be lowered at a slow pace due to resistance on the output shaft, I am considering...
  6. Q

    Impact and Detonation Calculations

    Can someone help me to calculate the approximate impact on the Earth (as in a mining explosion), of 1 ton of dynamite. And also the equivalent impact of say a 1 ton rock dropped from 10 meters. Trying to estimate this for writing purposes, I very roughly got: Impact of 1 ton of dynamite, Work...
  7. J

    Gravitation - gravity force, centripetal aceleration, work

    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...
  8. O

    Gravity force acting on masses and springs

    Hello Please why the mass m3 does not fall?
  9. P

    Is true force just "accepted" if it satisfies Newton law?

    So I understand the relationship between mass x acceleration=force but all that relationship tells me is "Whatever the force is to accelerate a given mass at a specific unit of acceleration = units of force, and we just accept whatever the unit of force is. example 1/ms² x 1 kg mass = 1 N...
  10. M

    A Can time be the cause of gravity's weakness and nonpolarity?

    Is it possible that the reason why gravity is the weakest fundamental force is because it is disappearing into the distant future? Similar to string theory's notion that gravity dissipates into other dimensions, only in this case it is time it dissipates through? Radon 220 and radium 224 nuclei...
  11. W

    Gravitational force confusing question

    I have this question on my practice test that I can't figure out. "Just as one jumps out of a plane what is their gravitational force given that the mass is 70kg." The thing is, for me to use the gravitational force formula I need to masses. The test only has the one. Am I missing something? Am...
  12. Stephanus

    Spaghettification near event horizon

    Dear PF Forum, Can we avoid spaghettification for some times, once we're inside event horizon? I choose a rather massive black hole, so the tidal force won't be so big at EH. Mass: 1 trillion solar mass Schwarzschild radius: 2.950 trillion KM What is the gravitational force at EH? I calculate...
  13. B

    Gravity force between Earth and Moon from this angle

    Homework Statement Hello the text is in swedish but ill try my best to translate, What it says is: Determine the resultant force on the moon with regard to thr gravitation force from the sun and the Earth when it's in this position shown in the figure [ picture http://m.imgur.com/AfJOVZo ] J...
  14. T

    Buoyant Force & Gravity Force find Fnet (Newtons Second Law)

    Homework Statement A 4 kg book sinks a distance of 5m in the ocean starting from rest. The volume of the book is 0.00266666666666667 m^3. We assume the velocity of the Earth is zero during the whole process, and gravity and the bouyance force are the only interactions of the book. (Note...
  15. C

    Gravity force: Isn't it just the shape of space?

    Isn't the force of gravity just a result of the shape of space as it is affected by masses within it? Why is it believed that it is a force associated with theoretical force particles "gravitons"? I can understand that the electric or magnetic force is a product of particles with fundamental...
  16. B

    Cause of Gravity Force: Explaining Monopolar Attraction

    Force is naturally associated with something acting on anything. Eletromagnetic forces are bipolares, i.e., charges are of opposite signals to atract one another. Why gravity is monopolar ? The einsteins elastic rubber example imply on a kind of hyerarchy of forces, so, it would possible that...
  17. 1

    A car is moving by gravity force

    Homework Statement In t=0 a car is free from it's chain and can fall freely through a inclined plane (10 degrees) rear wheels weight 500 lb each one and have an diameter of eight feet. Front wheel weights 800 lb and have a radius of 2 feet. The body of vehicle weights 9000 lb. Assume that...
  18. S

    Gravity Force Term: Exploring (1/2) in Fluid Mechanics

    This is not a problem statement this is not homework this is not a textbook exercise. This is my own question about a formula in a textbook. I was given an infraction because I did not post this here. Homework Statement Source: Fluid Mechanics 2nd ed. - P. Kundu, I. Cohen.pdf I am...
  19. O

    What generate the Gravity force from mass?

    When we look into the molecules, there are proton neutron and electrons, as we know there is an attracted force between positive and negative charges. Does anyone have any suggestions on what generate the Gravity force from mass? Thanks in advance of any suggestions
  20. D

    Special Cases for Gravity Force Inside Solid Objects

    ---------------------------------------------------------------------------- I know about the shell theorem and that the force of gravity due to the mass of the spherical shell is zero inside. I have some questions that may easily be answered for other special cases using the shell theorm and...
  21. P

    Can electromagnetism explain gravity?

    Hi all guys, for what I have understood from general relativity theory, gravity force is "just" a space-time distortion as a result of peculiar property of matter having mass. So it is not a real force, or saying with different words, if I'm in a lab without window, in a gravitational field...
  22. R

    How Does Gravity Influence the Movements of Planets and Moons?

    Why do specific object movement is conditioned by the gravity force? Why the moon is pulled by Earth and doesn`t move freely? Why the planets don`t move in different way but obey to the gravitacional force of Sun? Everybody knows that Earth moves around the sun for 1 year and travels for...
  23. P

    Tension of strings and gravity force help

    Homework Statement Q= 2800N G= 10m/s^2 s=35m t=10s __________ Fst=? (st-String tension) Can anyone help me with this, i have a test tomorrow And if anyone can give me the formula for the Tension force i'd be really grateful.
  24. M

    Gravity force probelm

    Homework Statement When the Earth, Moon, and Sun form a right triangle, with the Moon located at the right angle, as shown in the figure , the Moon is in its third-quarter phase. (The Earth is viewed here from above its North Pole.) Find the magnitude of the net force exerted on the Sun. Find...
  25. Q

    Exploring the Weakness of Gravity Force Compared to Electric Force

    The gravity force between ourselves and the objects around us is extremely small as gravity is a very weak force. The electric force is far stronger than the gravity force. Since we and the objects around us are composed of charged particles, why don’t we experience huge electrical forces...
  26. M

    Gravity force on a thrown ball problem

    A ball is thrown in the air at 44 m/s. How high does it go? How do you work this out?
  27. E

    Work done by the gravity force

    I have this question: A 28 lb suitcase is pulled up a frictionless plane inclined at 30 degrees to the horizontal by a force P with a magnitude of 18 lb and acting parallel to the plane. If the suitcase travels 15 ft along the incline, calculate: (a) the work done on the suitcase by the...
  28. W

    Gravity force on Jupiter problem

    At the surface of Jupiter's moon Io, the acceleration due to gravity is 1.81m/s^2 . A watermelon has a weight of 49.0N at the surface of the earth. In this problem, use 9.81m/s^2 for the acceleration due to gravity on earth 1.) What is its mass on the surface of Io? 2.) What is its...
  29. T

    Quantum gravity force violations

    Apart from C, P and T violation in weak interaction, do the same violations occur for the other three forces, in particular, the quantum gravity force?
  30. D

    Gravity force on zero distance

    How much will be the gravity force between two weights each of which with 1 kg at zero distance? If you ask Newton the answer will unconditionally be infinity but Archimedes would say extreme for sure but not necessary infinite. Here is why: The force in Archimedes’s physics is more like...