What is Force of gravity: Definition and 100 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. E

    I Force of gravity on JWST while orbiting L2

    When the Webb is at a point on its L2 orbit, (not at L2), what direction is the centrifugal force vector compared to the direction of the combined earth-sun gravity vector on the opposite side? Is the direction of this centrifugal vector ALWAYS parallel to the sun-earth plane? or is it always...
  2. kara123

    Newton's laws of motion -- Force of gravity on a skydiver

    I think you would do force of gravity= mass x acceleration acceleration of gravity= 9.8 m/s mass 75 kg 75kg x 9.8 m/s =735 N i don't know if that's right but i have no idea how to calculate it after he lands, any help would be greatly appreciated!
  3. A

    Find the attractive force of gravity between two objects

    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"...
  4. Boltzman Oscillation

    How does a the vertical force of gravity end in horizontal motion?

    When a stream of water falls perfectly vertical, some water hitting the surface will disperse horizontally. What is the force that causes this? References would be awesome!
  5. P

    B Force of gravity along the radial direction

    I am trying to work out the velocity of the ball in a loop in terms of theta from the horizontal (like a unit circle) as it loses contact with the track. And having a lot of trouble understanding this equation m*g*sin(theta) = m*v2/r and this explanation: The ball will leave the rail when...
  6. A

    How Does Apparent Weight Change for an Astronaut Near the Moon?

    Homework Statement What is the apparent weight of a 70-kg astronaut 3800 km from the center of the Earth's Moon in a space vehicle when a) Moving at a constant velocity b) Accelerating toward the Moon at 2.9 m/s^2? State direction in each case Homework Equations wt = m(g+a) wt = m(g-a) Fgr =...
  7. M

    Force of Gravity & Coulomb's Law Force Question

    Homework Statement Two small spheres of 15 g each are suspended from a common point by threads of length 35 cm. Each thread makes an angle with the vertical of 20 degrees. Each sphere carries the same charge. Find the magnitude of this charge. (The correct answer is: 0.58 μC)Homework Equations...
  8. A

    Finding net gravitational attractions in a triangle

    1. The problem is attached in a picture. I've done it five times and keep getting it wrong. The correct answer is also displayed in the picture. Thank you for any help. 2. Fg=Gm_1m_2/r^2 3. I calculated Fg between AB and BC (they are equal). So Fg=(6.67*10^-11)(4)(4)/(.10)^2=1.067*10^-10...
  9. Hilmy atha

    How much energy does the force of gravity apply to a bullet?

    Homework Statement A bullet was shot at 40m/s Elevation angle : 37° Bullet mass = 0.01 Kg Question : how much work is done by the force of gravity to the bullet since it was shot until it reaches the ground again Homework Equations mgh = E.Pot 1/2mv ^2 = E kinetic The Attempt at a Solution...
  10. P

    Conceptual Force of Gravity Acceleration 2 vs 3 objects

    Hello, I've been thinking about the nature of Newton's Laws and had a question about two scenarios where I'm noticing a difference in the way the problem is framed and the outcome. I cannot sleep because it is wracking my mind. Let me start by stating what I know to be true going into the...
  11. RoboNerd

    Question on force applied to an object hanging from a cord

    Homework Statement A ball of mass m hangs vertically from a massless string experiencing a tension T. What force is required to pull the ball out to an angle theta from the vertical? 1) mgsin(theta)2) mgcos(theta)3) mgtan(theta)4) 2mg tan (theta)5) mg/cos (theta) Homework Equations no...
  12. Mr Davis 97

    The force of gravity of two objects on a third?

    Homework Statement [/B] Imagine we have three masses, m1, m2 and m3. m2 is greater than m1. m3 is smaller than both. If we hold m1 and m2 in place without movement, and place m3 in the midpoint of the line adjoining m1 and m2, what will happen to m3? Homework Equations Newton's law of...
  13. A

    When is the force of gravity 0?

    Homework Statement Homework Equations Fg=Gm1m2/r^2 g=Gm/r^2 The Attempt at a Solution I am having trouble finding a way to start. I can't set the g to 0 because that would not let me solve for radius.
  14. H

    How High Must a Rocket Travel for Gravity to Halve?

    A rocket ship is moving away from the Earth after having been fired from a launch pad in Florida. At what point above the Earth's surface will the force of gravity be reduced to ½ of its original value? ------------------ Prior to this question I was given the equations to calculate the Force...
  15. oreo

    Weight or Force of Gravity: Which is Applied to a Man Lifting a Mass?

    I have a question. Suppose a man is lifting a Mass. The mass of course pushes it down. Now what is the force the mass is applying to hand of man is it Weight or Force of gravity because weight acts on mass itself. Then what we call it precisely?
  16. amjad-sh

    Force of Gravity: F=mg and MmG/h2(sqared)

    The force of gravity is F=mg.We know that that the gravitational force between Earth and object is F=MmG/h2(sqared).Can we say that mg=MmG/h2(sqared)?
  17. S

    Time of a falling object when the force of gravity isn't constant

    Homework Statement Distance from planet = 10^14 meters, Radious of the planet = 10^7 meters, mass of the object = 100kg g on the planet's surface = 10 m/s^2, g 10^14 meters away from the planets center = 2.5 m/s^2 Homework Equations Fg=G*m*M/r^2 The Attempt at a Solution I calculated the...
  18. M

    Question: What force will a 30 kg meteor experience at the same altitude?

    Homework Statement A 12 kg meteor experiences an acceleration of 7.2 m/s2, when falling towards the Earth. A) How high above the Earths’ surface is the meteor? B) What force will a 30 kg meteor experience at the same altitude? Starting to get more comfortable with my calculations. If there...
  19. V

    Normal force cancels out the force of gravity?

    Alright, so I know there will be a normal force pointing perpendicular to the surface and gravitational force, right? Gravitational force = mg But since normal force acts in "opposite direction to the gravitational force". Wouldn't normal force then cancel out the gravitational force? If it's...
  20. S

    Gravitational force between objects

    1. The problem statement, all variables and given/known dat Three solid spheres of lead, each of mass 9.8 kg, are located at three corners of a square with side lengths of 50 cm. A small object is released at the forth corner. Considering only the gravitational forces among the four objects...
  21. PaulMango

    Half the size and mass, stronger force of gravity?

    I've arrived at a non-sensical solution for a pretty simple thought experiment about gravity. Please let me know where my thinking is breaking down: Assume we have a cube of even density and a point mass on center of one of the sides. There is a force of gravity between the two of GmM/r^2...
  22. Ess_Elle

    Meteor Gravitational Field Question

    Homework Statement A 12 kg meteor experiences an acceleration of 7.2 m/s^2 when falling towards the earth. a) How high above the Earth's surface is the meteor? b) What force will a 30 kg meteor experience at the same altitude? Homework Equations Fg= Gm1m2/r2 m1m2 r2 = Gm1m2/Fg r =...
  23. H

    Direction of Force of gravity on two people, concept?

    I know that there exists a force of gravity between person A and person B that are action reaction pairs. My question is, is this gravitational field inherent in matter(i think higgs boson) look like an electrostatic field between matter? I ask this because, it seems that the moon and the...
  24. L

    The Force of Gravity Depends on Two Masses

    Hello. I don't have a specific homework problem but more of an ideology problem with my brain. According to Newton's law of gravitation (written below), the force of gravity is directly proportional to the masses of both the objects under consideration. Why, then, is the force on a cart that...
  25. S

    Kinematics - Velocity, force of gravity, terminal speed

    Hi everyone, I would really appreciate any advice on how to go about solving the following problem. I'm supposed to investigate it in a report. Homework Statement A paratrooper who jumps out of an aircraft moving in horizontal flight initially has the same horizontal velocity as the aircraft...
  26. S

    What is the average force of gravity between Earth and the moon?

    Show that the average force of gravity between Earth (mass = 6.0 X 10^24kg) and the moon (mass = 7.4X10^22 kg) is 2.1X10^20 N. The average earth-moon distance is 3.8 X 10^8 m
  27. J

    Can the force of gravity ever be measured on a single particle?

    I haven't taken the time, but I'm pretty sure the force would be too low to ever, ever be measurable. But has anyone ever measured the force of gravity, from at least an atom? I'm not meaning the effects of gravity upon the atom, I'm meaning the exertion of gravitational force from an atom, to...
  28. S

    Force of Gravity in a 2 Dimensional Universe

    I know that Edwin Abbott more than 100 years ago wrote about a hypothetical universe with only two dimensions. I wonder if the force of gravity could exist in such a universe(please no general relativity). How would the force of 2 masses vary with distance? Could there be stable orbits and would...
  29. M

    Relation between EMR & the force of gravity?

    We know that radio waves follow the curvature of the earth. Reason? Gravity (I think) The only logical thing I can think of is what Johann Heinrich Winkler discovered in mid 1800's; that when electricity is given multiple paths to choose from, it invariably chooses the best conductor (least...
  30. P

    Force of Gravity Just Prior to the Big Bang

    So I had a thought earlier regarding the moment just before the big bang, when the universe was infinitely small and infinitely dense, while still maintaining the estimated mass of 1.6 x 1060. Using the formula for gravitational force, my mass (68.2 kg) and the force holding me on Earth...
  31. D

    Force of gravity on one object caused by four objects

    1. A square of edge length s is formed by four spheres of masses, m1, m2, m3, and m4. What is the x-component and the y-component of the net gravitational force from them on a central sphere of mass m5. State your answers in terms of the given variables. (Use any variable or symbol stated above...
  32. P

    Can mass play a factor in the force of gravity on Earth?

    So I was thinking about the equation for the acceleration of gravity on earth, or g: m*g=G*M(earth)*m/d^2 I guess it's universally accepted that different masses on Earth's gravitational acceleration is 9.8m/s^2, regardless of the mass of the object. This is because the two "m"s cancel...
  33. A

    Solving for Density: Buoyant Force & Force of Gravity

    Homework Statement Homework Equations density = mass/volume FB = rhoo vog for a floating object F = mg The Attempt at a Solution Buoyant force = force of gravity due to the board rhoo vo = m vo = area*height submerged vo = 2.4*.05 vo = 0.12 m^3 volume of the board =...
  34. E

    Is the force of gravity constantly increassing?

    So I recently found out that gravity and mass are proportional and anything with mass has gravity, now I have another question, I am starting to wonder since the population of Earth is constantly increasing it would also mean the mass on Earth is also increasing (even a people who have died...
  35. K

    Force of gravity on magnetically levitating object?

    I just had a question regarding magnetic levitation.. If an object were to have a great enough magnetic force (via magnets of unequal strengths) to cause an object to be lifted while being held together by something that isn't rigid, like string, would putting force on the top object project...
  36. B

    I know the force of gravity inside a hollow sphere is 0, but

    We were never given an explanation in class. I remember in my high school physics class last year, our teacher told us this is true but never showed us why. All he said was that you had to integrate a function relating distance to mass, and the result would be a net force of 0 anywhere inside...
  37. L

    Force of Gravity Between Proton & Electron in Hydrogen Atom

    I started pondering random thoughts earlier today and this was one of them; what is the force of gravity between a proton and electron in a hydrogen atom? Using the equation to find this force (F = G\frac{}m_{}1 * m_{}2{}r^{}2) I came up with my answer. However I wanted to ensure that my math...
  38. P

    Force of gravity involving astrology

    Homework Statement People who believe in astrology think the positions of the planets at the time of birth have a large effect on the personality and destiny of the baby. The only known interaction between a planet and the baby is the force of gravity. Calculate the force of gravity (in...
  39. A

    Is force of gravity dependent on speed of one of the body?

    Is there any such relation as per general theory of relativity?
  40. S

    Force of gravity in relativity

    How can we calculate force of gravity between two objects using Einstein's relativity theory. Using Newton's method we can easily find attractive force between two objects by using formula f=g*m1*m2/r^2 But how can we calculate the force using Einstein's equation?
  41. S

    True mass, different weights, and the force of gravity

    Homework Statement An astronaut enters a rocket ship and gets blasted to another planet. The mass of the planet is 2.5 times as large as the mass of Earth, and the radius is 1.2 times as large as Earth's. If the astronauts scale at home says "60.0kg", what will it say on the new planet? In...
  42. Mordred

    Earths force of gravity measured in Dynes

    I have a copy of a 1923 physics book so here is a question from it lol " what is the force of gravity at the equator at sea level measured in Dynes ? " Another question is What is the definition of fusion in 1923 ? what is the model of the atom and size assigned to each of its...
  43. N

    What Is the Coefficient of Friction for Fred's Rollerblades?

    Fred (60 kg) is rollerblading at a velocity of 25 km/h [E] when he sees a broken glass bottle on the path ahead. He brakes and is slowed to a velocity of 8 km/h [E] in 4.2 s. What is the coefficient of friction between Fred's rollerblades and the ground? (Hint: Find FN and Ff first.) Given...
  44. N

    The Force of Gravity Question

    On Earth, the gravitational field intensity is 9.8 N/kg. Mercury has a mass of 3.28 x 1023 kg and a radius of 2.57 x 106 m. Calculate the gravitational field intensity on Mercury in N/kg. Given: g = 9.8 N/kg (on earth) m = 3.28 x 10^23 Kg d = 2.57 x 10^6m Required: g = ...
  45. D

    Acceleration with force of gravity and friction

    Homework Statement A block is placed against the vertical front of a cart. The coefficient of static frction between the block and the cart is \mus. What acceleration must the cart have in order that the block does not fall? How would an observer on the cart describe the behavior of the...
  46. A

    Calculating Work Done by Force of Gravity on a 0.245 kg Ball

    Homework Statement A 0.245 kg ball is thrown straight up from 2.20 m above the ground. Its initial vertical speed is 12.40 m/s. A short time later, it hits the ground. Calculate the total work done by the force of gravity during that time. Homework Equations 1/2m(v initial)2 + mg(h...
  47. S

    Force of Gravity question, with Newton's Law of Gravitation

    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...
  48. T

    Force of Gravity of Al on Mt. Everest

    Homework Statement In this problem find the force of gravity of Al. Al is standing at the top of Mt. Everest at an elevation of 8,848 m. Al has a mass of 58 kg. The Earth has a mass of 5.97e24 and a radius of 6.38e6m. What is the force of gravity acting on Al? Homework Equations F...
  49. C

    Understanding the Force of Gravity and Acceleration on a Planet's Surface"

    What is the acceleration due to gravity on the surface of a planet with mass 5.00 x 1023 kg and radius 3.00 x 107 m? If you need to, suppose that a block of mass 50 kg is at rest on the surface. Why does it not matter what the mass of the block is? a= Fnet/mass i don't know the Fnet
  50. C

    Force of Gravity: Mass Change Factors

    By what factor does the force change if a. The mass of the 10-kg ball is doubled? b. The mass of each ball is doubled? Fg=(Gm1m2)/r sqrd i know i can find the anser by using this but i don't know hoe to do it for (a) i don't have the masse of the second obj. so double of 10 is 20...