![]() ![]() He distinguished between the innate tendency of objects to find their "natural place" (e.g., for heavy bodies to fall), which led to "natural motion", and unnatural or forced motion, which required continued application of a force. Aristotle believed that motionless objects on Earth, those composed mostly of the elements earth and water, to be in their natural place on the ground and that they will stay that way if left alone. In Aristotle's view, the terrestrial sphere contained four elements that come to rest at different "natural places" therein. Īristotle provided a philosophical discussion of the concept of a force as an integral part of Aristotelian cosmology. Analysis of the characteristics of forces ultimately culminated in the work of Archimedes who was especially famous for formulating a treatment of buoyant forces inherent in fluids. The mechanical advantage given by a simple machine allowed for less force to be used in exchange for that force acting over a greater distance for the same amount of work. Since antiquity the concept of force has been recognized as integral to the functioning of each of the simple machines. See also: Aristotelian physics and Theory of impetus Aristotle famously described a force as anything that causes an object to undergo "unnatural motion" : 2–10 : 79 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. Only four main interactions are known: in order of decreasing strength, they are: strong, electromagnetic, weak, and gravitational. The Standard Model predicts that exchanged particles called gauge bosons are the fundamental means by which forces are emitted and absorbed. With modern insights into quantum mechanics and technology that can accelerate particles close to the speed of light, particle physics has devised a Standard Model to describe forces between particles smaller than atoms. By the early 20th century, Einstein developed a theory of relativity that correctly predicted the action of forces on objects with increasing momenta near the speed of light and also provided insight into the forces produced by gravitation and inertia. ![]() ![]() With his mathematical insight, Sir Isaac Newton formulated laws of motion that were not improved for nearly three hundred years. Most of the previous misunderstandings about motion and force were eventually corrected by Galileo Galilei and Sir Isaac Newton. A fundamental error was the belief that a force is required to maintain motion, even at a constant velocity. In part, this was due to an incomplete understanding of the sometimes non-obvious force of friction and a consequently inadequate view of the nature of natural motion. Philosophers in antiquity used the concept of force in the study of stationary and moving objects and simple machines, but thinkers such as Aristotle and Archimedes retained fundamental errors in understanding force. Stress usually causes deformation of solid materials, or flow in fluids. Pressure, the distribution of many small forces applied over an area of a body, is a simple type of stress that if unbalanced can cause the body to accelerate. ![]() Such internal mechanical stresses cause no acceleration of that body as the forces balance one another. In an extended body, each part usually applies forces on the adjacent parts the distribution of such forces through the body is the internal mechanical stress. 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 to the mass of the object.Ĭoncepts related 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. 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. It is measured in the SI unit of newton (N) and represented by the symbol F (formerly P). It can be a push or a pull, always with magnitude and direction, making it a vector quantity. moving from a state of rest), i.e., to accelerate. In physics, a force is an influence that causes the motion of an object with mass to change its velocity (e.g. ![]()
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