Tuesday, November 29, 2011

How To Succeed in Engineering: Dimensional Analysis and Tables

There have been too many instances where people in my engineering classes do NOT understand dimensional analysis or tables.  Sure, you may know how to do these things, but you need to be AWESOME at these things.  Some of you may not know what I'm talking about.  So let's have an introduction:

Dimensional Analysis
 I’ve loved dimensional analysis since middle school!  When I was 13, I could recite a TON of conversions (shows you how nerdy I was).  Here are some examples:

Convert 12 miles to meters.

If you buy a sweater that is $24, but 35% off, how much is the sweater?
Most people don’t know how to do these problems, at least not easily. 

Tips for the trade:
A dimension is a unit, which is like a number.  You can reduce the following: 5/5=1.  Well you can also do the following:  or  .

Think about other possibilities.  For instance,  .

Think about the unit actually represents.  Like area is just a two-dimensional length.  Volume is three-dimensional length.  Acceleration is the time derivative of speed which is the time derivative of length.  Okay, sure that was a little confusing.  But think about the bigger picture.  Here is a cool video to show you what I mean: Imagining the 10th Dimension.

Now about half (yes ½) of my upper division thermodynamics class was spent teaching us how to read tables.  And still people failed that class.  Sure, thermo goes beyond reading tables, but if you can’t read a table accurately, you are going to make silly mistakes on your tests.  And tests are your entire grade!

Tips for the trade:
Read lots of tables!  Like train tables!  I love sitting down and just looking at all the different times and thinking of different possibilities.  Another lame thing I like to do: read tables in the backs of textbooks.  It comes with surprises!  For instance, I found the specific heat for chicken and cake in the back of my Heat Transfer book.  Now, you can’t tell me THAT’s not interesting.

Use two pieces of paper to track your points.  Use one horizontally and the other vertically.  It’ll also help so you don’t strain your eyes.

Mark your point lightly with a pencil.  This has saved me many times.  Sometimes I’ll look back over the test and realize 1) my pencil point is in the wrong spot 2) I wrote down the number wrong.  It honestly helps you.

This whole blog post may seem like a "well, duh Serena."  But I'm telling you! Even my supervisors at my internships have converted wrong!  Be awesome at conversions, and then you can worry about the real "engineering."


  1. SO TRUE! I cannot tell you how many times I've been in a chemistry class and the students don't know how to convert units.

  2. Unit analysis has saved me so many times. I honestly think it should be a required separate class on its own. Even if I can't remember an equation, I rack up the partial credit by playing with the units and seeing how far I can get.