Force Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Defining "force" === Some textbooks use Newton's second law as a ''definition'' of force.<ref>{{Cite book |last1=Landau |first1=L. D. |author-link=Lev Landau |last2=Akhiezer |author2-link=Aleksander Akhiezer |first2=A. I. |last3=Lifshitz |first3=A. M. |author3-link=Evgeny Lifshitz |title=General Physics; mechanics and molecular physics |publisher=Pergamon Press |year=1967 |location=Oxford |edition= |isbn=978-0-08-003304-4 |url-access=registration |url=https://archive.org/details/generalphysicsme0000land_d9j0 }} Translated by: J. B. Sykes, A. D. Petford, and C. L. Petford. {{LCCN|67-30260}}. In section 7, pp. 12–14, this book defines force as ''dp/dt''.</ref><ref>{{Cite book |last1=Kibble |first1=Tom W. B. |last2=Berkshire |first2=Frank H. |title=Classical Mechanics |publisher=Imperial College Press |year=2004 |location=London |edition=5th |isbn=1860944248}} According to page 12, "[Force] can of course be introduced, by defining it through Newton's second law".</ref><ref>{{Cite book |last1=de Lange |first1=O. L. |last2=Pierrus |first2=J. |title=Solved Problems in Classical Mechanics |publisher=Oxford University Press |year=2010 |location=Oxford |edition= |isbn=978-0-19-958252-5}} According to page 3, "[Newton's second law of motion] can be regarded as defining force".</ref><ref>{{Cite book|last1=José|first1=Jorge V.|url=https://www.worldcat.org/oclc/857769535|title=Classical dynamics: A Contemporary Approach|last2=Saletan|first2=Eugene J.|date=1998|publisher=Cambridge University Press|isbn=978-1-139-64890-5|location=Cambridge [England]|oclc=857769535|author-link=Jorge V. José |page=9}}</ref> However, for the equation <math>\vec{F} = m\vec{a}</math> for a constant mass <math>m</math> to then have any predictive content, it must be combined with further information.<ref>{{Cite book|last1=Frautschi|first1=Steven C.|title=The Mechanical Universe: Mechanics and Heat|title-link=The Mechanical Universe|last2=Olenick|first2=Richard P.|last3=Apostol|first3=Tom M.|last4=Goodstein|first4=David L.|date=2007|publisher=Cambridge University Press|isbn=978-0-521-71590-4|edition=Advanced|location=Cambridge [Cambridgeshire]|oclc=227002144|author-link=Steven Frautschi|author-link3=Tom M. Apostol|author-link4=David L. Goodstein|page=134}}</ref><ref name=FeynmanVol1 />{{rp|((12-1))}} Moreover, inferring that a force is present because a body is accelerating is only valid in an inertial frame of reference.<ref name=Kleppner />{{rp|59}} The question of which aspects of Newton's laws to take as definitions and which to regard as holding physical content has been answered in various ways,<ref name="thornton-marion">{{cite book|first1=Stephen T. |last1=Thornton |first2=Jerry B. |last2=Marion |title=Classical Dynamics of Particles and Systems |edition=5th |publisher=Thomson Brooks/Cole |isbn=0-534-40896-6 |year=2004 |pages=49–50}}</ref><ref name=":0">{{cite book |author-last1=Landau |author-first1=Lev D. |title=Mechanics |author-last2=Lifshitz |author-first2=Evgeny M. |date=1969 |publisher=[[Pergamon Press]] |isbn=978-0-080-06466-6 |edition=2nd |series=[[Course of Theoretical Physics]] |volume=1 |translator-last1=Sykes |translator-first1=J. B. |author-link1=Lev Landau |author-link2=Evgeny Lifshitz |translator-last2=Bell |translator-first2=J. S. |translator-link2=John Stewart Bell}}</ref>{{Rp|pages=vii}} which ultimately do not affect how the theory is used in practice.<ref name="thornton-marion"/> Notable physicists, philosophers and mathematicians who have sought a more explicit definition of the concept of force include [[Ernst Mach]] and [[Walter Noll]].<ref>{{cite book |last=Jammer |first=Max |author-link=Max Jammer |title=Concepts of Force: A study in the foundations of dynamics |year=1999 |publisher=Dover Publications |location=Mineola, NY |isbn=978-0486406893 |pages=220–222 |edition=Facsim.}}</ref><ref>{{cite web |first=Walter |last=Noll |title=On the Concept of Force |url=http://www.math.cmu.edu/~wn0g/Force.pdf |publisher=Carnegie Mellon University |date=April 2007 |access-date=28 October 2013}}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page