Ubiquitous Drawing Errors for the Simple Pendulum

The so-called simple pendulum is found in all introductory physics textbooks, and one or more figures are usually devoted to its study. However, some textbook authors seem to exercise insufficient care in drawing the force diagrams for the motion, and mistakes in these drawings may confound the reader. In particular, there exists considerable confusion about the correct relative magnitude of the forces acting on the pendulum mass. This paper points out some of the common errors.