在科学中，力是对物体的推动或拉动，其质量可以使其改变其速度（加速）。力是一个向量，这意味着它既有大小又有方向。在方程和图中，力通常用符号F表示。例如牛顿第二定律中的着名方程：F = m·a其中F是力，m是质量，a是加速度。 SI单位的力是牛顿（N）。其他力量单位包括达因，千克力（千克力），poundal和磅力。虽然亚里士多德和阿基米德了解了力量是什么以及它们是如何起作用的，但伽利略·伽利莱和艾萨克·牛顿爵士描述了力量在数学上是如何运作的。牛顿运动定律（1687）预测了正常情况下力的作用。爱因斯坦的理论相对预测了力量的作用，因为动量接近光速。在本质上，基本力是重力，弱核力，强核力，电磁力和残余力。强力是将原子核中的质子和中子结合在一起的力量。电磁力负责相反电荷的吸引，类似电荷的排斥和磁铁的拉动。在日常生活中也遇到了非基本的力量。法向力作用于与物体之间的表面相互作用垂直的方向。摩擦力是一种抵抗表面运动的力量。非基本力的其他示例包括弹力，张力和与框架相关的力，例如离心力和科里奥利力。
In science, force is a push or a pull on an object with mass that can cause it to change its velocity (to accelerate). A force is a vector, which means it has both magnitude and direction. In equations and diagrams, a force is usually denoted by the symbol F. An example is the famous equation from Newton’s second law: F = m·a where F is force, m is mass, and a is acceleration. The SI unit of force is the Newton (N). Other units of force include the dyne, kilogram-force (kilopond), poundal, and pound-force. While Aristotle and Archimedes had a sense of what forces were and how they worked, Galileo Galilei and Sir Isaac Newton described how force works mathematically. Newton’s laws of motion (1687) predict the action of forces under normal conditions. Einstein’s theory of relatively predicts the action of forces as momentum approaches the speed of light. In nature, the fundamental forces are gravity, the weak nuclear force, the strong nuclear force, electromagnetic force, and residual force. The strong force is what holds protons and neutrons together in the atomic nucleus. The electromagnetic force is responsible for the attraction of opposite electric charge, repulsion of like electric charges, and the pull of magnets. There are also non-fundamental forces encountered in everyday life. The normal force acts in a direction normal to the surface interaction between objects. Friction is a force that opposes motion on surfaces. Other examples of non-fundamental forces include the elastic force, tension, and frame-dependent forces, such as centrifugal force and the Coriolis force.