Learning about basic hydraulics years ago
When I was in forestry school, I was in a course that was about building parks. So we had a section on plumbing and sanitary facilities, and the sewage part of the lessons featured, of course, a lot of shit jokes. The teacher was a rather rough-around-the-edges woman named Cathy, and she put up with a fair bit of our wisecracks.

Then we got to the part about plumbing.

For those of you who have never dealt with such things, a critical number to know is how far up a given pump can push a column of water- after all, you don't want an undersized pump that's not strong enough to get water to the sink. While pressure is expressed in pounds per square inch (or in Pascals over there, I suppose), pump pressure is often expressed in how many feet of water it can push. The term for this is "head". So a pressure drop in a system due to friction in the pipes or constrictions or whatever is known as "head loss", and of course there are other related terms- "required head", "minimum necessary head", and so on.

Cathy started out by telling us that anyone who made head jokes during the class would fail for the day. So we were struggling to keep our composure as she lectured us on all these terms, and generally succeeded.

She started doing an example problem on the board, saying that given this set of circumstances, you'd need this much head to achieve this much pressure, and so on. Therefore you'd need a pump capable of?...

Silence.

"Come on, guys, it's right here on the board! Three times twenty three equals?... Anybody?"

Strained silence.

"Sixty nine."

We all fell apart and she stood glowering for a moment before it clicked- and then she turned crimson and had to leave the room.

Class was done for the day.
( The Resident Loon Not a demographic. Do not measure., Thu 12 Jun 2008, 14:20, Reply)