Prove πR² using only beads and a ruler! I first saw this proof in an article by Russell Jay Hendel, Dowling College: http://bit.ly/LQlwQw minutephysics is now on Google+ - http://bit.ly/qzEwc6 And facebook - http://facebook.com/minutephysics And twitter - @minutephysics Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute! Music by Nathaniel Schroeder Thanks to Nima Doroud for contributions and to Perimeter Institute for support. http://www.perimeterinstitute.ca