kitchen table math, the sequel: dimensional analysis advice from Susan J

## Tuesday, July 17, 2007

### dimensional analysis advice from Susan J

As a former chemistry teacher I would say you cannot overemphasize an understanding of dimensional analysis.

For kids who don't see the point, ask them "backwards" questions such as how many feet are in an inch?

Also, have them do long chains such as determining how many centimeters in a mile. It's good to have figured these out in advance yourself so your student is instantly rewarded if they get the right answer.

Gary Carson said...

I managed to pass both intro chemistry and intro physics in college without learning anything at all about either subject just by being able to manipulate dimensions to arrive at an answer for exam questions. In one semester of Chem I even made a B and had no clue about the actual subject matter.

Catherine Johnson said...

good grief!

Catherine Johnson said...

well.... I'm glad to hear it

that was my intuition about these things

the instant I learned them I thought: THESE ARE GOLD

Catherine Johnson said...

kinda like CROSS MULTIPLICATION

Catherine Johnson said...

don't tell Steve I said that!

Anonymous said...

long time lurker here.

Gary, your comment is very revealing. Dimensional analysis is a deceptively powerful technique, and it should typically be your first defense against wrong answers. On multiple choice type tests, it can sometimes get you all the right answers.

Catherine Johnson said...

Dimensional analysis is a deceptively powerful technique, and it should typically be your first defense against wrong answers.

not so defensive to those of us who did not get a decent math education!

Catherine Johnson said...

hi, longtime lurker!

Tracy W said...

It's interesting, because in another way unit multipliers are just algebra.

Except for having to remember how many units there are in something. I can never remember how many feet there in a mile (NZ is metric).

Catherine Johnson said...

5280!

Catherine Johnson said...

Saxon has you spend A LOT of time using unit multipliers to convert between metric & English customary.

Catherine Johnson said...

Is it English customary??

Doug Sundseth said...

1 mile = 5280 feet = 1760 yards = 8 furlongs = 320 rods.

Unless it's a nautical mile, which is 1852 meters (precisely), 6076.115 ft, or quite close to 1 minute of longitude at the equator (its original definition).