I find that most engineering teachers do this, at least in the upper level classes and especially to see if the class is paying attention. However the classes w

I find that most engineering teachers do this, at least in the upper level classes and especially to see if the class is paying attention. However the classes where it is done to see if people are paying attention are more often than not the classes that have a bad teacher who frequently makes mistakes, such as my dynamics teacher (thank god for hibbeler).