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===== Derivation and Explanation of Center of Mass Lecture (15 minutes) =====

{{courses:lecture:cflec:central_forces_notes.pdf|Central Forces Notes}} Section 3

  * Derivation of the equation of motion for the center of mass for a system of particles.  The definition of the center of mass arises from this derivation--do not define it first.
  * Discuss that the concept of center of mass as it arises in the derivation corresponds to students' intuitive notion.
  * Discuss that geometric meaning of $\Vec R$, the position vector from the origin to the center of mass.  Many students are so quick to put the origin at the center of mass, that $\Vec R$ does not represent a concept that they have thought about.
  * Discussion of the meaning of the center of mass equation of motion.
  * Relating the center of mass equation found to the [[http://www.physics.oregonstate.edu/portfolioswiki/doku.php?id=activities:main&file=survivor|Survivor Outerspace Activity.]]
  * It is particularly helpful to connect the idea of center of mass position to other weighted averages (esp. if they have just done Spins and Waves).

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