Picking up on Mr. Weaver's comment in the "Draft" thread:
In engineering class, when studying trusses, very often a support member is a cable or rope within a structure, and a mistake that is often made by students is to have a compression load in the cable, which of course is impossible. The professors would always make the note on the student's calculations: "you can't push on a rope!"
In fluid flow there is the same analogy, although many have trouble dealing with it: "you can't pull on a fluid" That statement is entirely true, but in industry many think that you can pull on fluids, common misnomers like "vacuum drag of condensate into the condenser" or "suction" or "a pump pulling in suction flow" causing fluid to rise in a straw (or pump suction line). Fluids will not support any tensile stress, you cannot pull on a fluid. What causes fluid movement here is a higher pressure on the upstream end, PUSHING on the fluid. Of course gravity also plays in many fluid flow conditions.
... Pushing on a rope. Sounds like an existential crisis.