David Craig mentioned that bound/unbound vectors appear in engineering texts discussing statics. I have a few of those books on my shelf, and in one of them I encountered yet another couple unfamiliar terms.
Begin with a force that has a "line of action" and this force will act on a body at some intersection of the body and the line of action. To calculate the moment at point O (on the body), the moment is M = rxF where r is the vector from O to the line of action. Vector r points from O to *any point* on the line of action, which means the length of r will change depending on where it connects to the line of action of the force. The angle between r and F also changes as the point of action changes to any of the points along the line of action. No matter where the point of action occurs (as long as it is along the line of action of the force), the moment about O... M = rxF... is the same value.
Quoting from a book, but adding asterisks for emphasis... "... F has the properties of a *sliding vector* and can therefore act at any point along its line of action and still create the same moment about point O. We refer to F in this regard as being *transmissible*... "
The book also states that M is a *sliding vector* because it can be considered "... [to act] at any point along the moment axis."
Reference: Engineering Mechanics Statics and Dynamics, 5th Edition, R.C. Hibbeler, sections 4.2 and 4.3 beginning on page 97.
Regardless of what these are called, it was a bit of an eye opener for me to study the statics portions of some of these engineering texts. The torque situations studied are way more complicated than encountered in the typical calculus-based college physics courses, and I had not thought of some of the engineering ramifications of forces acting at various points on 3-D bodies supported at various other points, and whether the supports are rigid or rotatable or can slide, etc.
In this particular case, I had never thought of the idea described above... that once a line of action (also called line of force) is defined, it can act on an object by attaching to the object at any point along the line of action and will end up producing the same moment about O no matter what point of attachment (along the line of action) is chosen. I don't seem to find this idea in books such as Tipler/Mosca or Serway/Jewitt.
I don't think this is defining things to the nth degree. Rather, it is an attempt to understand which variables make a physical/engineering difference and which ones don't.
Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu