Blackburn pendulum

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A Blackburn pendulum is a device for illustrating harmonic motion, it was named after Hugh Blackburn —who described it in 1844. This was first discussed by James Dean in 1815 and analyzed mathematically by Nathaniel Bowditch in the same year.[1] A bob is suspended from a string that in turn hangs from a V-shaped pair of strings, so that the pendulum oscillates simultaneously in two perpendicular directions with different periods. The bob consequently follows a path resembling a Lissajous curve; it belong to the family of mechanical devices known as harmonographs.[2]

Mid-20th century physics textbooks sometimes refer to this type of pendulum as a Double Pendulum. See, for example, Francis Sears and Mark W. Zemansky: University Physics, Third Edition, Addison-Wesley Publishing Company, 1964.

An interesting artistic application of the Blackburn pendulum can be found here: [1].


  1. ^ L.P. Pook (2011). Understanding Pendulums: A Brief Introduction. Springer. 
  2. ^ Gregory L. Baker and James A. Blackburn (2005). The Pendulum: a case study in physics. Oxford.