# Moving toward authenticity

Consider the following question:

A dog running for a ball takes 4.6 seconds to reach the ball that lands 59 metres away. How fast did the dog run?

That is a fairly typical introductory physics problem, dealing with uniform motion. It is also the type of question used in grade 6 to practice the manipulation of fractions. So it’s an easy question. It is easy because all of the values are provided explicitly, and the formula to solve it is straightforward (v=d/t). When explicit values are given, a physics problem – even a more complicated one – devolves to a cookbook math problem: find the right recipe, apply the correct formulas, spit out the answer. The end result is an excessive reliance on explicit information, and a dissociation from the actual, authentic events.

It also leads to an over reliance on the math to make a question more challenging. Not that there is anything wrong with more challenging math, but that should not be the sole determination of difficulty.

So let me show you how I pose the same question:

How fast is my dog?

[stream flv=x:/www.teachscience.net/wp-content/uploads/2010/12/dog_run_1.flv embed=false share=true width=640 height=360 dock=true controlbar=over bandwidth=med autostart=false /]

(full res .mp4 here)

This is essentially the same question as above, but suddenly much more involved. And it has no “correct” answer – the best anyone can do with this is provide a reasonable value. The complexity arises from having to measure (or determine) values that are not given explicitly. Which is all of them (well, almost. There is a metre stick lying in the grass…). And as I have written before, having to make measurements requires a lot more in the way of critical thinking.

There are a number of ways a question like this can be analyzed, which I will cover in later posts.