Science, Tech, Math › Science Force Definition and Examples (Science) What Is a Force in Chemistry and Physics? Share Flipboard Email Print Martin Leigh, Getty Images Science Chemistry Physical Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 10, 2020 In science, force is the push or pull on an object with mass that causes it to change velocity (to accelerate). Force represents as 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 an equation from Newton's second law: F = m·a where F = force, m = mass, and a = acceleration. Units of Force The SI unit of force is the newton (N). Other units of force include dynekilogram-force (kilopond)poundalpound-force Galileo Galilei and Sir Isaac Newton described how force works mathematically. Galileo's two-part presentation of the inclined-plane experiment (1638) established two mathematical relationships of naturally-accelerated motion under his definition, strongly influencing how we measure force to this day. Newton's Laws of Motion (1687) predict the action of forces under normal conditions as well as in response to change, thus laying the foundation for classical mechanics. Examples of Forces In nature, the fundamental forces are gravityweak nuclear forcestrong nuclear forceelectromagnetic forceresidual force The strong nuclear force 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. Non-fundamental forces are also 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.