I wanted a good explanation for the difference between reciprocation and sinusoidal motion (For e.g. SHM). This question has been posted here due to many ambiguous and unclear explanations round the Web.


For a motion to be called simple harmonic, the force should be proportional and opposite to the displacement: $F = -kx$. Reciprocating motion is just a back-and-forth motion and per se, does not have to follow said law.

  • $\begingroup$ Well, in the last paragraph of en.wikipedia.org/wiki/Reciprocating_motion , There is a practical difference. Could you elaborate on that? $\endgroup$ – Shishir Maharana Jun 16 at 10:54
  • $\begingroup$ Uniform circular motion and simple harmonic motion are very closely related: the projection of a particle exhibiting $\textbf{uniform}$ circular motion performs a simple harmonic motion. byjus.com/physics/… That is what is said about the motion of the rotating part. The part of the connecting rod connected to the piston, however, does not exhibit a simple harmonic motion, because the angle of the rod changes continuously. $\endgroup$ – thunderbolt Jun 16 at 11:00
  • $\begingroup$ OK. Thanks a lot. :) $\endgroup$ – Shishir Maharana Jun 16 at 11:45

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