The moment about a point is expressed as, Recall the relationships associated with cross products, All other cross products are zero. Consider Figure 1 where someone is using a screwdriver to pry a paint can lid. To make things simple the coordinate system is rotated slightly. This is perfectly legitimate mathematically. Remember mathematics is a tool to make our job easier.
Force applied by the person pushing the screwdriver is, and that of the top is .
In this laboratory you will explore this concept in three dimensions. The laboratory apparatus is shown in Figure 2. The masses, which can be varied, may be placed at a variety of positions. This will require calculating a three-dimensional moment. A copy of the spreadsheet showing the calculation of the cross-product and net moment.