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.
Read more about Force: Development of The Concept, Pre-Newtonian Concepts, Newtonian Mechanics, Descriptions, Fundamental Models, Non-fundamental Forces, Rotations and Torque, Kinematic Integrals, Potential Energy, Units of Measurement
Famous quotes containing the word force:
“As a final instance of the force of limitations in the development of concentration, I must mention that beautiful creature, Helen Keller, whom I have known for these many years. I am filled with wonder of her knowledge, acquired because shut out from all distraction. If I could have been deaf, dumb, and blind I also might have arrived at something.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“Mathematics alone make us feel the limits of our intelligence. For we can always suppose in the case of an experiment that it is inexplicable because we don’t happen to have all the data. In mathematics we have all the data ... and yet we don’t understand. We always come back to the contemplation of our human wretchedness. What force is in relation to our will, the impenetrable opacity of mathematics is in relation to our intelligence.”
—Simone Weil (1909–1943)
“While I shall not vote for the prohibition amendment, I would like to see a good, wholesome expression of temperance sentiment.... Personally I do not resort to force—not even the force of law—to advance moral reforms. I prefer education, argument, persuasion, and above all the influence of example—of fashion.”
—Rutherford Birchard Hayes (1822–1893)