# Force

In physics, a force is any influence that causes an object to undergo a certain change, either concerning its movement, direction, or geometrical construction. It is measured with the SI unit of newtons and represented by the symbol F. In other words, a force is that which 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 can also be described by intuitive concepts such as a push or pull. A force has both magnitude and direction, making it a vector quantity.

The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional the mass of the object. As a formula, this is expressed as:

where the arrows imply a vector quantity possessing both magnitude and direction.

Related concepts to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque which produces changes in rotational speed of an object. Forces which do not act uniformly on all parts of a body will also cause mechanical stresses, a technical term for influences which cause deformation of matter. While mechanical stress can remain embedded in a solid object, gradually deforming it, mechanical stress in a fluid determines changes in its pressure and volume.

### Other articles related to "force":

Meteorology - History - Research Into Cyclones and Air Flow
... with air being deflected by the Coriolis force to create the prevailing westerly winds ... extent of the large scale interaction of pressure gradient force and deflecting force that in the end causes air masses to move along isobars was understood ... By 1912, this deflecting force was named the Coriolis effect ...
Knightmare - Life Force
... The life force was a combined clock and progress meter used to track the energy status of the dungeoneer (the main contestant) ... would often tell the team "You're wasting Life Force"), taking "damage" through being attacked by monsters or obstacles, taking the wrong route or making bad decisions ... In the first five series, the life force was a computer animated image of an adventurer wearing a helmet ...
Force - Units of Measurement
... The SI unit of force is the newton (symbol N), which is the force required to accelerate a one kilogram mass at a rate of one meter per second squared, or kg·m·s−2 ... The corresponding CGS unit is the dyne, the force required to accelerate a one gram mass by one centimeter per second squared, or g·cm·s−2 ... foot-pound-second English unit of force is the pound-force (lbf), defined as the force exerted by gravity on a pound-mass in the standard gravitational field of 9.80665 m·s−2 ...
... featuring the words Royal Australian Air Force, beneath which scroll work displays the Latin motto (shared with the Royal Air Force) Per Ardua Ad Astra ...
Lift (force)
... A fluid flowing past the surface of a body exerts surface force on it ... Lift is the component of this force that is perpendicular to the oncoming flow direction ... It contrasts with the drag force, which is the component of the surface force parallel to the flow direction ...

### Famous quotes containing the word force:

The body, what is it, Father, but a sign
To love the force that grows us, to give back
What in Thy palm is senselessness and mud?
Karl Shapiro (b. 1913)

Men have two ways of righting their wrongs, by force and by the ballot. Both are denied to women, one by nature, the other by man.
Ida A. Harper 1851–1931, U.S. women’s magazine contributor. Fireman’s Magazine, repr. In The Woman’s Magazine, pp. 423-5 (May 1887)

Awareness of the stars and their light pervades the Koran, which reflects the brightness of the heavenly bodies in many verses. The blossoming of mathematics and astronomy was a natural consequence of this awareness. Understanding the cosmos and the movements of the stars means understanding the marvels created by Allah. There would be no persecuted Galileo in Islam, because Islam, unlike Christianity, did not force people to believe in a “fixed” heaven.
Fatima Mernissi, Moroccan sociologist. Islam and Democracy, ch. 9, Addison-Wesley Publishing Co. (Trans. 1992)