# husoski

### "Your criteria doesn't match any questions"?

My lip goes into involuntary curls when I read this, but since I have been above median age (except, perhaps, in Boca Raton) for decades now, I have to ask...

Is this legitimate, now? Has "criterion" gone the way of "agendum" and "alumnus", or is this still considered ill-informed usage?

6 réponsesWords & WordplayIl y a 4 années### Electrostatics: Is this a fair question?

This problem from a recent edition of Halliday & Resnick (& whoever)...

In the x-y plane there are equal charges +q placed on the y axis at (0,D) and (0,-D). Let E(x) be the field at a point (x,0) on the x axis. Let a = x/D be the x position scaled to the y distance D.

(a) Find the value of a where E(x) = E(aD) is a maximum.

Note: This is eminently fair, and the answer is a = 1/√2. It's a pretty good elementary problem. The questionable part comes next:

Find the values of a where E is one half the maximum value. (b) and (c) ask for these two values. The Wiley website asks for something like 2% accuracy, and accepted a numerical solution obtained with the use of technology.

Is it fair to have a problem that can't be solved analytically using methods that the student has studied? Unless I'm missing something, this involves solving an unfactorable cubic, and nobody tortures lower-division math students with the cubic formula. They get an introduction to numerical integration in Calc I, typically, but most won't have taken a numerical analysis class.

So, is there a way to get a 2% answer to this without technology using methods that a student would be expected to have covered?

If not, is it sensible to even ask such a question? By today's standards, of course. When I took the course, it would have been unthinkable.

2 réponsesPhysicsIl y a 10 années### How many isosceles triangles on grid?

How many isosceles triangle can be made in the x-y plane that satisfy all of:

a. Integer coordinates,

b. Area = 9,

c. A vertex at the origin.

Two congruent triangles are different for this problem if they are not coincident. That is, if at least one vertex of the two triangles is not common to both.

This is motivated by an earlier question that I "pre-answered" and was prematurely awarded with a BA (undeserved). See:

3 réponsesMathematicsIl y a 1 décennie### SATA Power Connector Problem?

I ran into an odd thing yesterday when I was dusting out my system. After closing the hood and hooking up all the peripherals, I got a boot device error. The problem was that one of the SATA power connectors was disconnected. I reseated the connectors on both drives and they both feel a bit loose--much less insertion (or extraction!) force than I remember when building the system a little over a year ago. It seems like a mild problem to me and I wonder if it's a known problem with certain connectors, a thermal problem in the case, or what?

It's a CoolerMaster PS, around 500W, and WD Caviar 250G SATA drives.

2 réponsesDesktopsIl y a 1 décennie### How do I find the brand and model number of a shower valve?

This is the original valve installed in a new home around 1982. I can remove the handle and trim plate, but can't see any identifying information on the valve, plate or handle? It's a shower-only (no tub) single-valve setup: pull-push for on-off, twist for temperature control.

1 réponseDo It Yourself (DIY)Il y a 1 décennie