Section 10.1 Defining Rigid Structures
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In this chapter, we’re going to analyze the properties of rigid structures. We will consider a rigid structure to be a structure that consists of a single body that does not flex or bend. In practice, a rigid structure can be composed of many pieces, but with the restriction that the pieces are not intended to move relative to each other so that they behave as if they are a single body. Also, the reality is that all objects will flex and bend somewhat, but we are going to assume that the flexing is small relative to the size of the object, so that we can think of the object as not flexing at all.
Rigid Bodies and Forces.
There are many applications of physics where it is helpful to think about objects as rigid bodies. For example, buildings and bridges can be seen as rigid bodies for the purposes of thinking about how well they would hold up under loads and other types of strains.
We can think about the an object at many different levels. We can think about the body as a whole, or we can think of it as being multiple rigid pieces. As we allow objects to be built of more and more pieces, it results in more complex physics. When looking at the object as a whole, we are usually working with the external forces on the object. When looking at the object as multiple individual pieces, we’re usually talking about the internal forces on an object. If the rigidity is lost when thinking of the individual pieces, the object basically breaks. We will be spending some time looking at both situations.
