Velocities Of Rigidly-connected Points
Illustration for rigidly-connected points. "If two points are so connected that their distance apart is invariable and if their velocities are resolved into components at right angles to and along the straight line connecting them, the components along this line of connection must be equal, otherwise the distance between the points would change."
Peter Schwamb, S.B. And Allyne L. Merrill, S.B. Elements Of Mechanism (New York: John Wiley & Sons, Inc., 1905) 9
Courtesy the private collection of Roy Winkelman