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Explanation of Fundamental Forces - Succeed in Understanding Physics. Also refer to gravitational, electromagnetic, nuclear, strong, weak, attraction, repulsion, matter, General Relativity, Quantum Mechanics, graviton, photon, gluon, boson, electron, proton, charge, magnetic pole, Physical Science, Ron Kurtus, School for Champions. Copyright © Restrictions
Fundamental Forces
by Ron Kurtus (revised 23 September 2009)
There are several fundamental forces that affect the way that objects or particles of matter interact with each other at a distance. These forces do not require motion and direct contact, such as when a moving object collides with another. These forces apply to all matter from sub-atomic particles to galaxies of stars.
The fundamental forces are gravitational, electromagnetic and nuclear. Some classify the two nuclear forces—strong and weak—as individual fundamental forces. They vary in strength and distance at which they are effective.
Questions you may have include:
- What are the properties of the gravitational force?
- What are the properties of the electromagnetic force?
- What are the properties of the nuclear forces?
This lesson will answer those questions. There is a mini-quiz near the end of the lesson.
Useful tools: Metric-English Conversion | Scientific Calculator.
Gravitational force
Gravitation is the force of attraction between particles or objects of matter. It has the greatest reach or range but is also the weakest of the fundamental forces. The gravitational strength is only 6*10−39 of the strength of the strongest nuclear forces.
Note: 10−39 equals 1/1039, where 1039 is 1 followed by 39 zeros. That is a very small number.
The strength of the gravitational force decreases as the square of the distance between two objects. This means that if you triple the distance, the gravitation will be reduced by 1/9.
The force of gravitation is most apparent in objects of large mass, such as planets and stars. Gravitation is what keeps the Earth and other planets in orbit around the Sun.
Note: Gravity is defined as gravitation near the surface of the Earth.
The Theory of General Relativity explains the force due to gravitation as a result of the curvature of space caused by matter. The newer Theory of Quantum Mechanics explains gravitation as caused by the exchange of graviton particles between the masses.
Note: Although the concept of explaining forces that act at a distance as the exchange of particles is generally accepted in Quantum Mechanics, I find it hard to believe. It seems counterintuitive.
Although gravitation is only an attractive force, some scientists speculate that there may be a sort of anti-gravitation that causes objects to repel away from each other. Perhaps it is related to what is called "dark matter".
(See Gravitation for more information.)
Electromagnetic force
Electromagnetic force consists of the attraction and repulsion of materials consisting of electric charges, as well as magnetic materials.
Electric force
Electric charges can be positive (+) or negative (−), where like charges repel and unlike charges attract. Protons have a positive (+) charge and electrons have a negative (−) charge. Electric forces are what hold atoms and molecules together.
The strength of an electric force and a magnetic force drops off as the square of the distance between the charged particles.
(See Basics of Electricity for more information.)
Magnetic force
Magnetic poles can be north (or north-seeking) and south (or south-seeking). Like poles repel and unlike poles attract. Moving and spinning electrical charges create a magnetic field, depending on their direction o motion.
The strength of a magnetic force drops off as the square of the distance between the magnetic poles.
(See Magnetism for more information.)
Strength and cause
The relative strength of the electromagnetic force is 1/137 of the strong nuclear force.
At one time electromagnetic forces were explained as a property of space that consisted material called aether. The present explanation is the exchange of photon particles.
Nuclear forces
Nuclear forces are divided into what they call strong and weak forces.
Strong force
The strong force is the attraction that holds the nucleus of an atom together, overcoming the repulsive electrical force of the positive (+) charged protons.
The relative strength of the strong force is designated as 1. The range of this force is small, approximately the diameter of a medium-sized nucleus (10−15 m). Apparently, this force does not decrease by the inverse square as do the gravitational and electromagnetic forces. Instead, it just stops at its given distance.
The Theory of Exchange Forces designates the gluon as the "glue" that holds the nucleus together, through some sort of exchange between nuclear particles. (This seems counterintuitive and is not accepted by all physicists.)
Weak force
The weak force in a nucleus involves an exchange of W and Z vector boson particles. The strength of the weak force is 10−6 that of the strong force. Its range is only 10−18 m, which is about 0.1% of the diameter of a proton.
The purpose of the weak nuclear force apparently is to allow deuterium fusion to take place. This is necessary for our Sun and the stars to burn. Deuterium is a hydrogen isotope. It is also necessary for the creation of heavy nuclei and causes phenomena such as beta decay.
Summary
There are three fundamental forces that act at a distance. They are gravitational, electromagnetic and nuclear forces. Electromagnetic forces consist of electrical and magnetic forces. Nuclear forces consist of strong and weak forces.
See side menu for other Force topics
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Resources
The following resources provide information on this subject:
Websites
Fundamental Forces - Hyperphysical science
Books
Top-rated
books on Physical Science
Mini-quiz to check your understanding
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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