# New Paper Dance: “Investigating Systematic Uncertainty and Experimental Design with Projectile Launchers”

The week before last, I finished writing up a pedagogical paper I’ve been meaning to write for some time, and sent it off to The Physics Teacher. A couple of days ago, it occurred to me that I could probably post that to the arxiv. So I did, just before I left town for an extended weekend reliving my college days:

Investigating Systematic Uncertainty and Experimental Design with Projectile Launchers

The proper choice of a measurement technique that minimizes systematic and random uncertainty is an essential part of experimental physics. These issues are difficult to teach in the introductory laboratory, though: because most experiments involve only a single measurement technique, students are often unable to make a clear distinction between random and systematic uncertainties, or to compare the uncertainties associated with different techniques. In this paper, we describe an experiment suitable for an introductory college level (or advanced high school) course that uses velocity measurements to clearly show students the effects of both random and systematic uncertainties.

I’m not going to post anything else substantive this weekend, but if you’re interested in the teaching of introductory physics, I hope you’ll find it worthwhile. If not, well, there are a lot of other blogs out there…

## Comments

1. #1 magista
August 26, 2011

Cool. I’ll give it a try this semester (grade 11 physics) and let you know how it went.

2. #2 CCPhysicist
August 27, 2011

Interesting paper. I, too, have seen the “digital is perfect” belief in the labs. I am sure it arises because of calculators, but I should ask them on a start-of-class quiz.

In your case, of course, the problem is that they are unaware of the concept of “reaction time”. the readout on the watch is, AFAIK, at worst chopped at the last digit. Digital multimeters are an entirely different story, since the last digit is wrong on the ones we use. I have them measure the same thing (voltage or current) on different scales to open their eyes to the fact that no rounding is taking place.

3. #3 JM
August 28, 2011

Unrelated to this post, unless someone else sees pedagogy in hurricanes–

I hope you and your families are safe as Hurricane Irene passes.

4. #4 Kate Nepveu
August 28, 2011

JM, thanks for the concern; all is well.

5. #5 anon
August 29, 2011

Another point that you didn’t mention in your paper is that the stopwatch method requires two observations, while the meter-stick method requires only one.

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