In this article we refer to the somewhat surprising fact that questions connected with the mechanics of such popular physical models as the simple and conical pendulum seem to be difficult not only for secondary school students but even for those taking introductory university courses in physics. Two tests concerning both the simple pendulum and the conical pendulum were examined by groups of 50 students. We give a brief analysis of their unsatisfactory results as well as a correct presentation of the problem at the secondary school level.