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Gravitation, or simply gravity, is the attraction between two bodies. All objects in space attract each other with a certain degree of force, but due to the vast distances between them, the force is too faint to be noticed in most circumstances. Albert Einstein formulated the theory of gravitation between 1907 and 1915. Newton's Law of Universal Gravitation was universally acknowledged in the 20th century. The gravitational force, according to Newton, is caused by matter. Gravitation is defined as the force exerted by the earth's surface. In fact, it is a natural phenomenon in which all objects with mass or energy, such as planets, stars, galaxies, and even light, are drawn together.
Key Terms: Gravity, Gravitational Force, Gravitation, Free Fall Motion, Centripetal Force, Centre of Gravity
What is Gravitation?
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Gravitation is the force that pulls two masses toward each other in physics. Every particle of substance in the universe exerts a gravitational attraction on every other particle. It is, in reality, a force that is expressed by the acceleration of two free material particles or substances, or radiant-energy quanta, toward one another.
The terms gravitation and gravity are sometimes used interchangeably to describe the attraction that exists between all things that have energy or mass. While gravity is the force that pulls an item toward the Earth, gravitation is a more broad term for this fundamental force. "Every particle in the cosmos attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of their separation." according to Sir Isaac Newton's 17th-century Law of Gravitation.
Gravitation Examples
We've all seen the phenomenon of an apple falling from a tree to the ground's surface, but what causes the apple to fall to the ground remains a mystery.
You may have noticed that when you throw a ball up, it returns to you and falls into your hand. Similarly, raindrops, or water droplets, fall on the ground during a rainy season. If you look at all of this, you'll notice that things are descending towards the earth's surface due to some force. So these are the examples we find in the terrestrial environment, as well as in the universe if we look at planetary motion.
The planets are held in a particular orbit by some force. We all know that the planets orbit each other in a specific way. As a result, some forces hold the planets in their specific orbits. As a result, gravitation is to blame for all of these occurrences. Gravitation is defined as the force exerted by the earth's surface.
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Universal Law of Gravitation (Newton’s Law of Gravitation)
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Newton's Law of Gravitation is a fundamental law that describes the forces of interaction between two point masses. It is a universal law. If we are given two masses, m1 and m2, and the distance between them is d, then these two masses will attract each other according to the notion of gravity, and the force will be determined by Newton's law of gravitation. It is stated in this law that the masses. "Force is inversely proportional to the square of the distance between the two masses," as the expression goes.
F ∝ m1m2 -----------------------(1)
F ∝ 1/r2 ----------------------------(2)
When these equations are combined, we get Force equals proportionate G and m1, m2 by r square, which is the expression.
F ∝ m1m2/r2
F = G × m1m2/r2
"The square of the distance between the two objects divided by the global gravitational constant times the mass of each object."
The Universal Gravitational Constant is abbreviated as G. (G = 6.67 x 10-11 is the value.)
m1 and m2 are the mass of the two objects, respectively and d is the distance between the object's centers in a straight line.
Newton’s Law of Gravitation: Applications
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Newton’s law of gravitations holds true in several situations involving objects with masses, big or small. We can apply it to any objects that are separated by a very large distance. Given below are the applications of Newton’s Law of Gravitation:
→ The estimation of binary star masses is one of the most important uses of Newton's law. A binary star is a pair of stars orbiting each other around a shared mass center.
→ Any irregularity in a star's velocity suggests that it could be another star or a planet orbiting the stars. A wobble is a term for this regularity in a star's motion.
Gravitation: Gravity
Gravity is an all-pervasive universal force that pulls a body towards the Earth's core or any other mass-bearing physical body. It is the force that keeps us on the ground and prevents us from flying into space. Although gravity has an infinite range, its effects weaken as things get further away.
Gravity is best characterized by the general theory of relativity, which depicts gravity as the result of masses traveling along geodesic lines in a curved spacetime due to an uneven distribution of mass, rather than as a force. The most dramatic example of this curvature of spacetime is a black hole, from which nothing, including light, can escape once past the event horizon. For most applications, however, Newton's law of universal gravitation, which describes gravity as a force that attracts any two bodies toward each other and has a magnitude proportional to the product of their masses and inversely proportional to the square of their distance, is a good approximation.
The weakest of the four fundamental interactions in physics is gravity. As a result, it has no discernible effect at the subatomic particle level. On the macroscopic scale, however, it is the main interaction that causes the formation, shape, and trajectory (orbit) of astronomical bodies.
Read more: Gravity: Discovery, Definition, Calculations, Facts
Gravitation: Acceleration due to Gravity
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Acceleration gained by any object due to the attractive gravitational force between two objects is called acceleration due to gravity. The standarizes value of gravity of earth is denoted by (G).
As F = mg and F = G x (Mm/R2)
So, g = G x (Mm/R2)
Putting the values of G = 6.673 x 10−11 N m2 Kg−2
⇒ M(mass of Earth) = 6 x 1024 kg and R = 6 x106 m , to get the value of gas ≈ 9.8 m/s2.
This is the acceleration caused by gravity, as well as the acceleration experienced by any freely falling body as it approaches the Earth.
The value of g changes as the radius of the Earth changes.
Centre of Gravity
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As we all know, every particle is pulled to the earth's core. A body consists of a large number of particles. The gravitational attraction acting on these particles can be considered parallel to one another because the body is small in contrast to the earth.
A single downward force acting vertically can be replaced by a single downward force acting through a fixed spot known as the body's centre of gravity. The resulting force is equal to the weight of the body. As a result, regardless of the body's location, the centre of gravity is the point through which the weight of the body acts.
The geometrical centre of gravity of bodies with a regular shape and constant density is at the geometrical centre of the body. The geometrical centre of gravity of bodies with a regular shape and constant density is at the geometrical centre of the body.
Universal Gravitational Constant
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Newton's Law of Gravitation is expressed mathematically as
F = (Gm1m2)/d2
If m1 = m2 = 1 and d =1, then F = (G x 1 x 1)/(12)
So, F = G
As a result, the gravitational force between two unit masses separated by a unit distance can be defined as the universal gravitational constant.
Also, G = (Fd2)/(m1m2)
The SI unit of universal gravitational constant G = (Nm2)/(kg2) as N is the SI unit of force, m is the SI unit of distance and kg is the SI unit of mass respectively. In 1798, Sir Henry Cavendish measured the experimental value of G to be as 6.6734 x 10-11 Nm2/(kg2)
Gravitation: Gravitational Force
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The gravitational force binds the earth, the moon, and any other massively big object together. This is the total weight of everything. All objects on Earth use a "downward" gravitational force that pulls them towards the earth's centre. On Earth, the gravitational force is always equal to the object's weight.
Fgrow = mg
In this case, g = 9.8 N/kg
M stands for mass (in kg)
Gravity is built up of Gravitations, which are Quantum Particles.
Read more: Gravitational Force and Law of Gravitation: Introduction and Explanation
Centripetal Force
The centripetal force acts on an object moving in a circular motion and is directed towards the object's centre of rotation. When an object moves at a constant speed along a circular path, it is subjected to a centrifugal force that accelerates it towards the centre.
Read more: Centripetal Force Formula: Definition, Difference and Solved Examples
Free Fall Motion and Weightlessness
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Free Fall Motion- Gravitational acceleration is constant at g = 9.8 m/s2 when an object is in free fall. The value of g is independent of mass, meaning that in free fall, any object, large or tiny, feels the same acceleration due to gravity. For freely falling objects, all three equations of motion are true, just as they are for uniform motion. While the convention sign for g is positive towards the earth, g is negative when facing away from earth.
The force that pulls an object towards the earth is called weight. The sensation of being completely or nearly completely weightless is referred to as weightlessness. It can also be described as a state of being devoid of gravity.
Weightlessness- It is a state of free fall in which the gravitational influence is neutralised by the centrifugal force generated by orbital flight, resulting in no gravitational force acting on the objects. It's best described as a state in which the body is completely unaware of its own weight. An apple, for example, will not feel its weight if it falls from a tree. The sensation of weightlessness that anyone can have during a free fall is known as weightlessness.
Mass and Weight- The inertia of an object is measured by its mass, which is constant throughout the universe. As the value of g changes, so does the weight of an object. Weight is nothing more than the Earth's gravitational pull on an object = mg.
The weight of an object on the Moon is one-sixth that of an object on Earth.
Density and Relative Density-
Density- The density of a substance is the mass per unit volume of the substance. The density of a substance remains constant when certain criteria are met. As a result, density is one of the differentiating features of a material, and it may be used to determine the purity of any substance.
D = \(\frac{M}{V}\)
Where D stands for density, M for mass, and V for volume.
Read more: Unit of Density: Definition, Formula, Example and Applications
Relative Density- The ratio of a substance's density to the density of water at 4°C is called relative density. Water is supposed to have a relative density of one.
The relative density of a substance is equal to the substance's density divided by the density of water at 4°C. The relative density of a substance is also defined as the mass of the substance divided by the volume of an equal volume of water. Because it is a ratio of two similar quantities, the relative density has no unit.
Thrust and Pressure
Thrust is the force applied on an item perpendicular to the surface. Thrust has a different effect depending on the contact area. The thrust per unit area is the pressure. The SI unit of pressure is pascal (Pa). When a force is applied to a smaller area, it exerts more pressure than when the same force is applied to a wider area.
Buoyancy and Archimedes Principle
Buoyancy, also known as buoyancy force, is the force that causes any object floating in a fluid medium to rise. The weight of the item on which the buoyant force is operating determines the size of the force. The differential in pressure above and below the object as a result of a change in medium causes it.
The Archimedes Principle describes the link between the apparent weight of an object submerged in water and the weight of the water displaced by it, as first described by Archimedes. This positive correlation has been found through factors such as Buoyant Force.
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| Related Topics | |
|---|---|
| Force and Motion | Weightlessness |
| Pressure | Difference Between Mass and Weight |
Things to Remember
- Every particle of matter in the universe exert gravitational attraction on every other particle. Gravitation is a force that occurs when two free material particles or substances, or radiant-energy quanta, accelerate toward each other.
- According to Newton's Law of Gravitation, every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of their distance.
- F = G [M1M2]/r2 is the formula for gravitational force while F = GMm/r2 is the equation for Newton's law of gravitation.
- In SI units, the gravitational constant is 6.67 * 10-11 Nm2 kg-2, while 6.67 * 10-8 dyne cm2 g-2 is the value in CGS Unit.
- The gravitational force is a central force that acts along the line connecting the q of two masses, and its direction is determined solely by their relative positions to the source mass.
Sample Questions
Ques: What is the difference between the Gravitational Field and the Gravitational Force, and how do you explain it? (3 Marks)
Ans: The force of gravity is proportional to both the source and test masses, whereas the field is solely a feature of the source mass. The Earth is the only source of this vector field. It is frequently referred to as gravitational force per unit mass since it quantifies how much force the planet Earth will apply on a unit mass.
Ques: We can't see gravity on other objects, so why can't we perceive it on ourselves? (2 Marks)
Ans: All objects in the cosmos attract each other with a certain degree of force, but due to the vast distances between them, the force is too faint to be noticed in most circumstances. Furthermore, while gravity's range is infinite, the effect weakens as objects travel further away.
Ques: What exactly do you mean when you say "gravity" and "gravitation"? (2 Marks)
Ans: Because of the force of attraction that exists between everything with mass or energy, the terms gravity and gravitation are frequently misunderstood. We can say that the force of gravity is the pull of an item toward the Earth and that gravitation is the broad term for this fundamental force.
Ques: What significance does the universal law of gravitation have? (2 Marks)
Ans: The gravitational attraction of the earth ties terrestrial objects to it.
The attraction force that exists between any two mass objects is explained by this law.
Tides arise in the ocean due to the force of attraction between the moon and the ocean water.
All planets make an elliptical rotation around the sun.
Ques: What's the Difference Between Einstein's Gravity Theory and Newton's Gravity Theory? (2 Marks)
Ans: Einstein viewed gravity as a curvature in a 4-dimensional space-time fabric proportional to object masses, whereas Newton described gravity as a force expressed mutually between two things in relation to their masses.
Ques: Is there gravity in space? (2 Marks)
Ans: We are surrounded by gravity. It shapes planetary orbits, the solar system, and even galaxies. The gravity of the Sun reaches all the way to the solar system's outermost reaches, keeping the planets in their orbits. Earth's gravity keeps the Moon and human-made satellites in orbit.
Ques: Is the value of g the same everywhere? (2 Marks)
Ans: No, depending on where you are on the planet's surface, the value of g changes. Gravity accelerates less at the equator than at the poles. This is because g is inversely proportional to radius, and the radius of the earth is smaller towards the poles and larger at the equator.
Ques: What Does Gravity Have to Do With Black Holes? (3 Marks)
Ans: A black hole is an astronomical object having a large amount of mass packed into a small volume, resulting in an area of enormous gravity. A black hole's immense gravitational attraction prevents anything from escaping. It prevents even light from passing through it. Event horizons are the surfaces of black holes. They mark the point at which the escape velocity required to break free from its gravitational pull is greater than the speed of light. As a result of the universe' speed limit, matter and radiation can fall into a black hole but cannot escape.
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