In physics, a force is any external agent that causes a change in the motion of a free body, or that causes stress in a fixed body. It can also be described by intuitive concepts such as a push or pull that can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or which can cause a flexible object to deform. Force has both magnitude and direction, making it a vector quantity. Newton's second law states that an object with a constant mass will accelerate in proportion to the net force acting upon and in inverse proportion to its mass. Equivalently, the net force on an object equals the rate at which its momentum changes. See also thrust.

Forces acting on three-dimensional objects may also cause them to rotate or deform, or result in a change in pressure or even change volume in some cases. The tendency of a force to cause changes in rotational speed about an axis is called torque. Deformation and pressure are the result of stress forces within an object.

Since antiquity, scientists have used the concept of force in the study of stationary and moving objects. However, descriptions of forces by Aristotle incorporated fundamental misunderstandings, which, despite advances made by the third century BC philosopher Archimedes from studies of simple machines, persisted for many centuries. By the seventeenth century, Sir Isaac Newton corrected these misunderstandings with mathematical insight that remained unchanged for nearly three hundred years. By the early 20th century, Einstein in his theory of general relativity successfully predicted relativistic adjustments to Newton's model for gravity by ushering in the concept of a space-time continuum.

The recent theory of particle physics known as the Standard Model associates forces at the level of quantum mechanics. The Standard Model predicts that exchange particles called gauge bosons are the fundamental means by which forces are emitted and absorbed. Only four main interactions are known: in order of decreasing strength, they are: strong, electromagnetic, weak, and gravitational. High-energy particle physics observations made during the 1970s and 1980s confirmed that the weak and electromagnetic forces are expressions of a more fundamental electroweak interaction.

From Wikipedia under the GNU Free Documentation License
Mon Sep 7 07:18:36 2009

What are the physical forces that act on an airplane?
Q. What are the physical forces that act on an airplane? For Example: Gravity, Normal force, etc. Please be specific when giving answers. I would also like to know about the safety risks associated with flying, and please focus on the physics of an airplane. Really appreciate any help!
Asked by AYALEWNATOR - Sat Mar 15 12:27:09 2008 - - 2 Answers - 0 Comments

A. There are 4; Lift Thrust Weight Drag Lift must be larger than weight and thrust must be larger than drag for the airplane to fly. Some physical risks are metal fatigue, weather, pilot error...
Answered by Blue Sky - Sat Mar 15 12:32:03 2008

What force or forces constitute the fundamental source of energy that generates wind movement and circulation?
Q. 8 Please only respond if you are positive of your answers please, i cannot afford to get any questions wrong thanks! What force or forces constitute the fundamental source of energy that generates wind movement and circulation? Choose one answer. a. Pressure differences in the atmosphere b. Radiant energy of the Sun c. Coriolis Effect d. All of the above
Asked by Jack H - Sat Mar 7 23:32:12 2009 - - 1 Answers - 0 Comments

A. I am 99.9% sure that the answer is d. All of the above. Pressure differences in the atmosphere generate wind movement by pushing wind from high pressure to low pressure. Radiant energy from the Sun generates wind movement by creating uneven heating of the Earth's atmosphere and surface. The Coriolis Effect circulates wind because the air moves over the surface of the Earth while the planet itself is rotating under it.
Answered by Press Your Luck - Wed Mar 11 20:42:14 2009

What are the top 10 largest military forces in the world?
Q. I know China has the largest armed forces in the world, but I have had trouble finding information on other countries and the amounts of soldiers that they maintain.
Asked by yaykob - Fri Jun 29 21:55:11 2007 - - 9 Answers - 0 Comments

A. It probably goes China (PRC) India US Russia North Korea South Korea Pakistan Iran Turkey Vietnam Of course, size doesn't equal effectiveness - though the US and South korean forces would be the highest quality. North Korea would certainly have the lowest quality forces among on the list - barely a quarter would be at all effective other than as human fodder. The force size reflects the places the regions most of them occupy - Vietnam has been invaded by China, so would feel the need for a large force on that count; Turkey has a border with Iraq and Syria; South Korea faces the North Korean army, and so on. The US force structure is built to stabilise the globe (you can argue about whether it does this, but this is the reason for its size) [cont.]
Answered by Adam - Fri Jun 29 22:05:40 2007

From Yahoo Answer Search: "Forces"
Thu Sep 24 01:13:21 2009

See also:

  • World War OneWorld War One
    members.fortunecity.com
    Causes and effects of this conflict,the fronts, documents, and includes analysis of participant armies and navies.
  • Chemical Warfare During WWIChemical Warfare During WWI
    mitretek.org
    Chronicles the antecedents of chemical warfare, the development of chlorine gas, and the means of delivering these weapons.
  • WW1 Tanks and CarsWW1 Tanks and Cars
    mailer.fsu.edu
    The history of the development of the tank, other armored vehicles, and their impact with images.
Custom search only Forces sites:

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Wed Aug 19 20:14:12 2009
How the Air Force Is Solving Its 3 Biggest Problems - Popular Mechanics
news.google.com
How the Air Force Is Solving Its 3 Biggest Problems

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The Air Force has been knocked around recently. The service has generated some bad press about the way it operates, flies, fights and plans for the future. ...

New refueling jets to be fully loaded with high-tech equipment Nextgov

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DeJesus' illness forces lineup shuffle - MLB.com
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DeJesus' illness forces lineup shuffle

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new york -- Left fielder David DeJesus remained out of the Royals' lineup and manager Trey Hillman did some shuffling, moving Mitch ...



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Check the most glamorous Armed Forces in the China 60th ... - Bawaal - [ Technology Simplified ] (blog)
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Check the most glamorous Armed Forces in the China 60th ...

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No offense and all due respect to the fairer sex but this regiment of Chinese Army a civilian reserve force under China's secretive military is one to die ...



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From Google News Search: "Forces"
Fri Oct 2 19:54:36 2009

US Forces Trailer jpg
armed-assault-zone.com
US Forces Trailer jpg
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Worthplaying com have released a 3min long video of Arma showing off the US Forces The video weighs in at 59mb and is good quality footage

forces jpg
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forces jpg
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Reviews forces of nature usually I avoid chick movies like the plague but I like Sandra Bullock and Ben Affleck is fun to watch on screen Also the trailer made it seem like the movie might be

Americas Army Special Forces 2 jpg
linux.softpedia.com
Americas Army Special Forces 2 jpg
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Screenshot 2 of America s Army Special Forces FireFight 2 5 0 click below to see the full size image

From Yahoo Image Search: "Forces"
Sat Sep 26 13:01:17 2009

Conservatives4Palin.com: The Guardian Obliquely Hints at Dark ...
conservatives4palin.com
Conservatives4Palin.com: The Guardian Obliquely Hints at Dark ...

(David L Riddick (aka The Aged P))

Mon, 28 Sep 2009 15:09:01 GM

Michael Tomasky (aka Dan Brown?) at the Guardian gives an outline on the sad death of Bill Sparkman then ends with a cliff-hanger hinting at darker . forces. ...he doesn't say but Guardianistas will be able to read the hidden runes. ...

McChrystal Afghanistan Assessment: More Forces Or "Mission Failure"
huffingtonpost.com
McChrystal Afghanistan Assessment: More Forces Or "Mission Failure"

The Huffington Post News Team

Mon, 21 Sep 2009 00:11:33 GM

Washington the White House is considering expanding counterterror operations in Pakistan to refocus on eliminating al-Qaida instead of mounting a major military escalation in Afghanistan. Two senior administration officials said ...

The Duck of Minerva: Security Forces Deployed Acoustic Cannon ...
duckofminerva.blogspot.com
The Duck of Minerva: Security Forces Deployed Acoustic Cannon ...

Charli Carpenter

Sun, 27 Sep 2009 22:53:01 GM

"LRAD creates increased stand off and safety zones, supports resolution of uncertain situations, and potentially prevents the use of deadly . force. ... We believe this is highly preferable to the real instances that happen almost every day ...

From Google Blog Search: "Forces"
Tue Sep 29 10:04:23 2009