Pulleys and Gears

The most complicated machines often rely on a few simple principles oftechnology such as wheels springs screws ramps and wedges. This seriesexplores these techn... » 

The most complicated machines often rely on a few simple principles oftechnology such as wheels springs screws ramps and wedges. This seriesexplores these technologies by relating them to common machines in our everydayworld from bedsprings to skateboards to zippers. Numerous fact files offerreaders fast facts and other pertinent information. «