Gaya
Dina fisika, gaya téh nyaéta tarikan atawa dorongan anu bisa ngabalukarkeun hiji obyék nu boga massa diakselérasi (gerak tambah gancang atawa tambah laun). Gaya boga badag jeung arah tujuan, anu ngajadikeun gaya salaku kuantitas véktor. Nurutkeun Hukum gerak Newton kadua, hiji obyék kalayan massa nu tetep bakal diakselérasi (tambah gancang atawa tambah laun gerakna]] proporsional jeung gaya bérésih (néto) anu nimpah kana éta obyék sarta babanding tibalik jeung massana. Gaya anu nimpah kana obyék tilu diménsi bisa ogé ngabalukarkeun obyék kasebut muter atawa ngalaman deformasi, atawa ngahasilkeun parobahan tekenan. Kacondongan hiji gaya pikeun ngabalukarkeun puteran (akselerasi sudut) sabudeureun hiji sumbu disebut torsi. Deformasi jeung tekenan mangrupa hasil tina gaya-gaya strés dina jero hiji obyék.

Since antiquity, scientists have used the concept of force in the study of stationary and moving objects. These studies culminated with the descriptions made by the third century BC philosopher Archimedes of how simple machines functioned. The rules Archimedes determined for how forces interact in simple machines are still a part of physics. éarlier descriptions of forces by Aristotle incorporated fundamental misunderstandings which would not be corrected until the seventeenth century by Isaac Newton. Newtonian descriptions of forces remained unchanged for néarly three hundred yéars.

Current understanding of quantum mechanics and the standard model of particle physics associates forces with the fundamental interactions accompanying the emission or absorption of gauge bosons. Only four fundamental interactions are known: in order of decréasing strength, they are: strong, electromagnetic, weak, and gravitational. High-energy particle physics observations made during the 1970s and 1980s confirmed that the wéak and electromagnetic forces are expressions of a unified electroweak interaction. Einstein in his theory of general relativity explained that gravity is an attribute of the curvature of space-time.

Pre-Newtonian concepts 

Since antiquity, the concept of force has been recognized as integral to the functioning of éach of the simple machines. The mechanical advantage given by a simple machine allowed for less force to be used in exchange for that force acting over a gréater distance. Analysis of the characteristics of forces ultimately culminated in the work of Archimedes who was especially famous for formulating a tréatment of buoyant forces inherent in fluids.

Aristotle provided a philosophical discussion of the concept of a force as an integral part of Aristotelian cosmology. In Aristotle's view, the natural world held four elements that existed in "natural states". Aristotle believed that it was the natural state of objects with mass on Earth, such as the elements water and éarth, to be motionless on the ground and that they tended towards that state if left alone. He distinguished between the innate tendency of objects to find their "natural place" (e.g., for héavy bodies to fall), which led to "natural motion", and unnatural or forced motion, which required continued application of a force. This théory, based on the everyday experience of how objects move, such as the constant application of a force needed to keep a cart moving, had conceptual trouble accounting for the behavior of projectiles, such as the flight of arrows. The place where forces were applied to projectiles was only at the start of the flight, and while the projectile sailed through the air, no discernible force acts on it. Aristotle was aware of this problem and proposed that the air displaced through the projectile's path provided the needed force to continue the projectile moving. This explanation demands that air is needed for projectiles and that, for example, in a vacuum, no projectile would move after the initial push. Additional problems with the explanation include the fact that air resists the motion of the projectiles.

These shortcomings would not be fully explained and corrected until the seventeenth century work of Galileo Galilei, who was influenced by the late medieval idéa that objects in forced motion carried an innate force of impetus. Galiléo constructed an experiment in which stones and cannonballs were both rolled down an incline to disprove the Aristotelian theory of motion éarly in the seventeenth century. He showed that the bodies were accelerated by gravity to an extent which was independent of their mass and argued that objects retain their velocity unless acted on by a force, for example friction.

Newtonian mechanics 

Isaac Newton is the first person known to explicitly state the first, and the only, mathematical definition of force—as the time-derivative of momentum: . In 1687, Newton went on to publish his Philosophiae Naturalis Principia Mathematica, which used concepts of inertia, force, and conservation to describe the motion of all objects. In this work, Newton set out three laws of motion that to this day are the way forces are described in physics.

References

Bibliography

Tumbu luar 
 Video lecture on Newton's three laws by Walter Lewin from MIT OpenCourseWare
 A Java simulation on vector addition of forces
 Force Unit Converter

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