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Gravitation

Universal Gravitation Equation

Applications of Universal Gravitation Equation

Gravitational Escape Velocity

Influence of Gravitation in the Universe

Explanations of Gravitation

Gravitation and General Relativity

Effect of Dark Matter and Dark Energy on Gravitation

Gravity topics

Force of Gravity

Gravity Equation Comes From Universal Gravitation

Effect of Mass on Acceleration Due to Gravity

Gravitational Potential Energy

Artificial Gravity

Derivations

Overview of Derivation of Gravity Equations

Derivation of Velocity-Time Gravity Equations

Derivation of Distance-Time Gravity Equations

Derivation of Velocity-Distance Gravity Equations

Falling objects

Overview of Gravity Equations for Falling Objects

Velocity Equations for Falling Objects

Distance Equations for Falling Objects

Time Equations for Falling Objects

Effect of Gravity on Sideways Motion

Thrown downward

Overview of Gravity Equations for Objects Projected Downward

Velocity Equations for Objects Projected Downward

Distance Equations for Objects Projected Downward

Time Equations for Objects Projected Downward

Thrown upward

Overview of Gravity Equations for Objects Projected Upward

Velocity Equations for Objects Projected Upward

Distance Equations for Objects Projected Upward

Time Equations for Objects Projected Upward


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Explanation of Gravitation - Succeed in Understanding Physics. Also refer to Law of Universal Gravitation, fundamental forces, Isaac Newton, matter, attraction, force, mass, gravity, Einstein, relativity, dark matter, physical science, Ron Kurtus, School for Champions. Copyright © Restrictions

Gravitation

by Ron Kurtus (revised 26 September 2009)

Gravitation is the force that attracts objects toward each other. It is one of several fundamental forces of matter. Its strength is weak compared to the other forces, but its range is far-reaching.

The concept of that matter attracts other objects was formulated in 1687 by Isaac Newton as the Law of Universal Gravitation. This force of attraction is defined in the theory’s Universal Gravitation Equation, which states that the gravitational force is proportional to the masses of the two objects and inversely proportional to the square of distance between them. Gravity is considered a special case of gravitation for objects near the Earth.

This theory has been superseded by newer theories of gravitation, such as Einstein’s General Theory of Relativity and theories concerning Quantum Mechanics and dark matter.

Questions you may have include:

This lesson will answer those questions. There is a mini-quiz near the end of the lesson.

Useful tools: Metric-English Conversion | Scientific Calculator.

Gravitation is a fundamental force

Gravitation is one of four fundamental forces that affect the way that objects or particles of matter interact with each other at a distance. The fundamental forces are, in order of strength: strong nuclear, electromagnetic, weak nuclear and gravitational.

Comparing the forces gives a good perspective on the role of gravitation.

Strong nuclear force

The strong nuclear force is the attraction that holds the nucleus of an atom together, overcoming the repulsive electrical force of the protons within the nucleus.

The relative strength of the strong nuclear force is designated as 1. The range of this force is small, approximately the diameter of a medium-sized nucleus (10−15 m), after which it becomes too small to have an effect.

Electromagnetic force

Electromagnetic force consists of a combination of electric and magnetic forces.

Electric force

Electrical charges can be positive (+) or negative (−), where like charges repel and unlike charges attract each other.

Magnetic force

Moving and spinning electrical charges create a magnetic field, depending on their direction or motion. Magnetic poles can be north (or north-seeking) and south (or south-seeking). Like poles repel and unlike poles attract.

Strength and range

The relative strength of the electromagnetic force is 1/137 of the strong nuclear force. The range of the electromagnetic force is unlimited, but its strength drops off as the square of the distance between the charged particles.

Weak nuclear force

The weak force in a nucleus allows deuterium fusion to take place, which is necessary for our Sun and the stars to burn. The strength of the weak force is 10−6 that of the strong force, and its range is only 10−18 m, which is about 0.1% of the diameter of a proton.

Gravitation

Gravitation is the force of attraction between particles or objects of matter. It is the weakest of the fundamental forces, with a gravitational strength of only 6*10−39 of the strength of the strong nuclear force at a sub-nuclear distance.

Note: 10−39 equals 1/1039, where 1039 is 1 followed by 39 zeros. It is a very small number.

However, at distances beyond the sub-nuclear range, the strength of gravitation is much larger than the nuclear forces, which are essentially zero at those distances.

Since gravitation primarily concerns very large quantities of matter, such as planets and stars, its effect overshadows that of the stronger electromagnetic force, which operates on a much smaller level and at shorter distances.

Law of Universal Gravitation

The Law of Universal Gravitation (also called the Theory of Universal Gravitation) states that all objects are attracted toward other objects, due to a force called gravitation. This includes everything from subatomic particles to massive stars and planets.

Universal Gravitation Equation

Newton formulated the Universal Gravitation Equation, which allows the calculation of the force between two objects. The equation is:

F = GMm/R2

(See Universal Gravitation Equation for more information on the subject.)

Confusion concerning gravity

There is sometimes confusion between the expressions gravity and gravitation.

Gravity is defined as gravitation on or near the surface of the Earth. It is a special application of gravitation. The expression is also used for other objects in space, such as gravity of the Moon, gravity of the Sun or of the other planets, provided the planet is named.

(See Force of Gravity for more information on the subject.)

Gravitation is universal, while gravity is specific to the object. It is the force near the surface.

Further development

Although the Universal Gravitation Equation can explain many phenomena, some astronomical anomalies required a better solution.

General Theory of Relativity

It wasn't until the early 1900s that Albert Einstein gave another interpretation of the gravitation in his General Theory of Relativity. He stated that gravitation was the result of the curvature of space around matter and not due to some force.

This theory says that a "straight line" in space curves or bends toward matter. An object traveling along this line—even a ray of light—will then seem to be attracted toward the matter. The Universal Gravity Equation is just an approximation of a more complex relativistic equation.

One proof of this idea was first seen when position of stars seemed to shift as their light passed near the Sun.

Quantum Mechanics

Recently there have been new theories that the force of gravity is caused by graviton particles or by gravity waves. These theories satisfy rules of Quantum Mechanics that Einstein's concepts didn't.

Dark matter

There is also a theory that there exists some sort of "dark matter" that repels instead of attracts, resulting in anti-gravitation.

Summary

Gravitation is one of the fundamental forces of matter, being much weaker than the strong nuclear force but affecting objects at much greater distances.

Isaac Newton formulated the Law of Universal Gravitation, stating that all matter attracts other matter to it. This force of attraction is defined in the theory’s Universal Gravitation Equation. Gravity is a special case of gravitation for objects near the Earth.

Einstein’s General Theory of Relativity and new theories concerning Quantum Mechanics and dark matter bring other explanations for gravitation.

Answers to Readers' Questions

See the Side Menu for more Gravitation and Gravity topics


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Resources

The following resources provide information on this subject:

Websites

Acceleration due to Gravity Calculations - from Western Washington University

Gravitation and Gravity Resources

Books

Top-rated books on Simple Gravity Science

Top-rated books on Advanced Gravity Physics


Mini-quiz to check your understanding

1. What is the difference between gravitation and electromagnetic forces?

Gravitation only works at small distances, as opposed to the electromagnetic force

They are the same force with different names

Gravitation only attracts while the electromagnetic force attract or repel

2. What is the difference between gravitation and gravity?

They are different spellings of the same word

Gravitation attracts and gravity repels

Gravity is gravitation on or near the Earth

3. What was one proof that gravitation is due to the curvature of space?

Light passing by huge masses such as the Sun was deflected

No one has figured out how to prove it yet

A ball thrown in the air follows a curved path

If you got all three correct, you are on your way to becoming a Champion in Physics. If you had problems, you had better look over the material again.


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