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:
“The mind is the terriblest force in the world, father,
Because, in chief, it, only, can defend
Against itself. At its mercy, we depend
Upon it.”
—Wallace Stevens (1879–1955)
“Some sepulcher, remote, alone,
Against whose portal she hath thrown,
In childhood, many an idle stone—
Some tomb from out whose sounding door
She ne’er shall force an echo more,
Thrilling to think, poor child of sin!
It was the dead who groaned within.”
—Edgar Allan Poe (1809–1849)
“Taking men into the union is just the kindergarten of their education and every force is against their further education. Men who live up those lonely creeks have only the mine owners’ Y.M.C.As, the mine owners’ preachers and teachers, the mine owners’ doctors and newspapers to look to for their ideas. So they don’t get many.”
—Mother Jones (1830–1930)