Don't Panic with Mechanics! (PDF)

1. In Full Possession of Our Mental Forces And Moments: Statics (S. 1-3)

Imagine yourself sitting somewhere in a train compartment of the InterRegional Express between the German towns of Aurich and Visselhövede (the latter, located between Hannover and Bremen, can be pronounced much easier after a few shots of tequila, but Dr. Hinrichs can also manage this without the help!). After spending a few hours in the same position in this cramped seating arrangement, a slight pain in your posterior region will involuntarily manifest itself.

This can be attributed to a compressive force. Despite the pain, your willpower to keep from moving within the chosen coordinate system (e.g. rail car No. 234) actually triumphs! And already we have a static system! Statics is namely the science dealing with the action of forces on bodies at rest. And since we didn`t have to wait around for Einstein to know that a body under uniform motion can also be considered at rest, the laws of statics can also be applied to bodies or systems moving at constant speed, such as in our example with the train (assuming that it is moving considerably slower than the speed of light).

In all areas of mechanics, even the most elementary relationships can sometimes be a real poser because in some way or another they seem to elude our power of imagination. Another reason is the fact that we always try to solve a problem on the basis of our own experience combined with supposed logic. In this respect, mechanics can play some pretty nasty tricks on us (Dr. Hinrichs professes not to have experienced this phenomenon.) Let`s have a look at Fig. 1 (above). It shows a firmly fastened (fixed), massless rope whose free end is being pulled by exactly one Newton (a force of one Newton (1N) corresponds to the force needed to hold up approximately 0.1 kg).

Here the rope is assumed to be massless so that we do not have to take any vertical forces into account. The same rope is shown in Fig.

Dr. Nikolaus Hinrichs and Dr. Oliver Romberg received their Ph.D.'s in mechanical engineering from the University of Hannover. Besides research activities in this special area they were teaching Mechanics over a period of more than 10 years. They are quite aware of the problems when Mechanics and Students meet. Today Dr. Hinrichs is European Patent and Trademark Attorney, Göttingen. Dr. Romberg works as project manager in space technology, Bremen.

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"Auf Englisch, mit viel Witz und so mancher auflockernder Zeichnung beweisen die Autoren, dass die Grundlagen der Statik, Elastostatik und Kinetik ganz und gar nicht so trocken sind, wie wir immer dachten."
engine, 02/2006