phy. : force = mass * acceleration

Which means that the units of measurement for force (metric) are:

kilogram * meter
--------------------------
second * second

This means that the "weight" (pounds) used in America and England is a force (mass * the acceleration of gravity) whereas in Europe (and many other places) the mass (kilograms) alone is used to measure how heavy people are.

The mass unit in the English foot-pound-second system is called (ready for this) : the Slug. (not widely used, or even heard of; it's essentially being phased out) It's equal to 32.2 pounds or 14.6 kilograms.

The force unit in the metric system is : the Newton (widely used and fairly well known.)

In Ultimate Frisbee, the force is the direction the defensive team attempts to force the offensive team to throw to. The basic idea is that the mark stays on one side of the player with the disc, making it impossible, or at least harder, to throw to that side of the field. Then the rest of the defenders don't have to worry about covering their men as much on that side of the field, and can stand slightly to the strong side of their men. This looks like this:

Capital O has the disc, o is offense, d is defense.
```

|-----------------------------------------------------|
|							|
|							|
|							|
|							|
|							|
|-----------------------------------------------------|
|							|
|							|
|		Od	do-dump				|
|							|
|							|
|							|
|							|
|	strong side	d  o		weak side	|
|			d  o				|
|			d  o				|
|			d  o				|
|			d  o				|
|							|
|							|
|							|
|							|
|							|
|							|
|-----------------------------------------------------|
|							|
|							|
|							|
|							|
|							|
|-----------------------------------------------------|

```

Notice how the defenders are standing to the left of the offense. This means that any offensive player who cuts to the strong side is going to have to beat a defender who has a couple of steps on him already. On the weak side, the offensive player has a couple of steps, but it is much harder to throw to that side. The force is a pretty basic concept in frisbee defense. If you screw it up while you're on the field, people will scream "WRONG FORCE!!! WRONG FORCE!!!!" at you to remind you that you should be standing on the other side of your man. The force can be toward either sideline, and some teams will force middle, meaning that the mark always stands with his back to the sideline, trying to force the offense to throw towards the middle of the field. Sometims you will want to force straight up, or stand directly in front of the player you are marking in order to deny them the huck throw.

Webster gives us a definition of "force" in war or in card games but not a physical one.

Physicists give us a way to calculate force but there does not appear to be a good definition for what it is. I suppose that "force" can be considered a "primitive" concept that should be understood implicitly, but if we were hard-pressed to define it, I suppose

The fundamental effect of an object on the Universe, resulting from the object's existence, causing it to affect other objects.
or
A fundamental phenomenon of nature, which, when applied to an object, causes the object to move in a well-defined direction, alters the object's path of motion, or overcomes another force applied in an opposing direction.
will have to do, even though the latter will make holists wince. Physicists can later quantify things an point out that such a "tendency to move" is really an acceleration and is proportional to the object's inertia or mass. Then they can get into relativity. We've at least passed the buck onto the poor slob who has to define motion.

Our macroscopic notions of "force" are the effects we see from countless interactions between pairs of particles (wavefunctions) at the quantum-mechanical level: potential energy builds up between two particles, until there is enough energy to spontaneously create another pair, which travels from one to the other, changing the trajectories of both particles:

```   \             /
\           /
\         /
o~~~~~~~o
/         \
/           \
/             \
```

All of our day-to-day experience comes from innumerable little catastrophes of this sort, almost all of which are photons scattering pairs of electrons in our bodies' atoms.

The Standard Model of physics currently defines three "interactions" which cause forces to be exerted on objects:

Physics describes dozens of other "forces" which are really special cases of the above three interactions: things sich as centripetal forces, Van der Waals forces. Other, more complex effects such as the "Coriolis effect" or the "centrifugal effects" are erroneously termed as forces.

A notable exception is dark energy (sometimes called antigravity), not observed in our local environment, but which must exist due to cosmological inflation and the fact that the expansion of the universe is accelerating. This may be a special case of gravity, arising from Albert Einstein's cosmological constant.

It should be apparent from the second definition given above that force is a vector concept: The notion of a "direction" wouldn't be necessary if forces couldn't cancel each other out. At each point of the universe, then, each of the fundamental forces are is added up from all other points of the Universe and a final "result" vector is produced, the direction the object will accelerate. This gave rise to the field concepts of physics which are still useful in our macroscopic world. The field concept brings up notions of action at a distance, which in our macroscopic world, things like gravity and magnetism appear to be.

Quantum physics describes forces as derived from vector bosons emitted by particles and intercepted by other particles, changing their relative energy balances. The field concept lives even here, however: It is plausible to construct as a model of physics, consisting of only forces, with particles existing only as specific wavefunctions in these Universe spanning force fields.

There are at least three different units of force:

• The newton (kg*m/s2) an MKS SI unit.
• The dyne (g*cm/s2), a cgs SI unit.
• The pound from the English system of measurement used primarily in the United States. This unit was arbitrarily derived from the relative weight of objects at the Earth's surface.

Force (?), v. t. [See Farce to stuff.]

To stuff; to lard; to farce.

[R.]

Wit larded with malice, and malice forced with wit. Shak.

Force, n. [Of Scand. origin; cf. Icel. fors, foss, Dan. fos.]

[Prov. Eng.]

To see the falls for force of the river Kent. T. Gray.

Force, n. [F. force, LL. forcia, fortia, fr. L. fortis strong. See Fort, n.]

1.

Strength or energy of body or mind; active power; vigor; might; often, an unusual degree of strength or energy; capacity of exercising an influence or producing an effect; especially, power to persuade, or convince, or impose obligation; pertinency; validity; special signification; as, the force of an appeal, an argument, a contract, or a term.

He was, in the full force of the words, a good man. Macaulay.

2.

Power exerted against will or consent; compulsory power; violence; coercion.

Which now they hold by force, and not by right. Shak.

3.

Strength or power war; hence, a body of land or naval combatants, with their appurtenances, ready for action; -- an armament; troops; warlike array; -- often in the plural; hence, a body of men prepared for action in other ways; as, the laboring force of a plantation.

Is Lucius general of the forces? Shak.

4. Law (a)

Strength or power exercised without law, or contrary to law, upon persons or things; violence.

(b)

Validity; efficacy.

Burrill.

5. Physics

Any action between two bodies which changes, or tends to change, their relative condition as to rest or motion; or, more generally, which changes, or tends to change, any physical relation between them, whether mechanical, thermal, chemical, electrical, magnetic, or of any other kind; as, the force of gravity; cohesive force; centrifugal force.

Animal force Physiol., muscular force or energy. -- Catabiotic force [Gr. down (intens.) + life.] Biol., the influence exerted by living structures on adjoining cells, by which the latter are developed in harmony with the primary structures. -- Centrifugal force, Centripetal force, Coercive force, etc. See under Centrifugal, Centripetal, etc. -- Composition of forces, Correlation of forces, etc. See under Composition, Correlation, etc. -- Force and arms [trans. of L. vi et armis] Law, an expression in old indictments, signifying violence. -- In force, or Of force, of unimpaired efficacy; valid; of full virtue; not suspended or reversed. "A testament is of force after men are dead." Heb. ix. 17. -- Metabolic force Physiol., the influence which causes and controls the metabolism of the body. -- No force, no matter of urgency or consequence; no account; hence, to do no force, to make no account of; not to heed. [Obs.] Chaucer. -- Of force, of necessity; unavoidably; imperatively. "Good reasons must, of force, give place to better." Shak. -- Plastic force (Physiol.), the force which presumably acts in the growth and repair of the tissues. -- Vital force Physiol., that force or power which is inherent in organization; that form of energy which is the cause of the vital phenomena of the body, as distinguished from the physical forces generally known.

Syn. -- Strength; vigor; might; energy; stress; vehemence; violence; compulsion; coaction; constraint; coercion. -- Force, Strength. Strength looks rather to power as an inward capability or energy. Thus we speak of the strength of timber, bodily strength, mental strength, strength of emotion, etc. Force, on the other hand, looks more to the outward; as, the force of gravitation, force of circumstances, force of habit, etc. We do, indeed, speak of strength of will and force of will; but even here the former may lean toward the internal tenacity of purpose, and the latter toward the outward expression of it in action. But, though the two words do in a few cases touch thus closely on each other, there is, on the whole, a marked distinction in our use of force and strength. "Force is the name given, in mechanical science, to whatever produces, or can produce, motion."

Nichol.

Thy tears are of no force to mollify This flinty man. Heywood.

More huge in strength than wise in works he was. Spenser.

Adam and first matron Eve Had ended now their orisons, and found Strength added from above, new hope to spring Out of despair. Milton.

Force (?), v. t. [imp. & p. p. Forced (?); p. pr. & vb. n. Forcing (?).] [OF. forcier, F. forcer, fr. LL. forciare, fortiare. See Force, n.]

1.

To constrain to do or to forbear, by the exertion of a power not resistible; to compel by physical, moral, or intellectual means; to coerce; as, masters force slaves to labor.

2.

To compel, as by strength of evidence; as, to force conviction on the mind.

3.

To do violence to; to overpower, or to compel by violence to one;s will; especially, to ravish; to violate; to commit rape upon.

To force their monarch and insult the court. Dryden.

I should have forced thee soon wish other arms. Milton.

To force a spotless virgin's chastity. Shak.

4.

To obtain or win by strength; to take by violence or struggle; specifically, to capture by assault; to storm, as a fortress.

5.

To impel, drive, wrest, extort, get, etc., by main strength or violence; -- with a following adverb, as along, away, from, into, through, out, etc.

It stuck so fast, so deeply buried lay That scarce the victor forced the steel away. Dryden.

To force the tyrant from his seat by war. Sahk.

Ethelbert ordered that none should be forced into religion. Fuller.

6.

To put in force; to cause to be executed; to make binding; to enforce.

[Obs.]

What can the church force more? J. Webster.

7.

To exert to the utmost; to urge; hence, to strain; to urge to excessive, unnatural, or untimely action; to produce by unnatural effort; as, to force a consient or metaphor; to force a laugh; to force fruits.

High on a mounting wave my head I bore, Forcing my strength, and gathering to the shore. Dryden.

8. Whist

To compel (an adversary or partner) to trump a trick by leading a suit of which he has none.

9.

To provide with forces; to reenforce; to strengthen by soldiers; to man; to garrison.

[Obs.]

Shak.

10.

To allow the force of; to value; to care for.

[Obs.]

For me, I force not argument a straw. Shak.

Syn. -- To compel; constrain; oblige; necessitate; coerce; drive; press; impel.

Force, v. i. [Obs. in all the senses.]

1.

To use violence; to make violent effort; to strive; to endeavor.

Forcing with gifts to win his wanton heart. Spenser.

2.

To make a difficult matter of anything; to labor; to hesitate; hence, to force of, to make much account of; to regard.

Your oath once broke, you force not to forswear. Shak.

I force not of such fooleries. Camden.

3.

To be of force, importance, or weight; to matter.

It is not sufficient to have attained the name and dignity of a shepherd, not forcing how. Udall.