an ungodly speed

On a recent unit test, I asked my grade 12s to
(a) calculate the orbital speed MIR (or the Hubble), (3 marks)
(b) the period of its orbit, (1 mark) and
(c) explain whether their answers to (a) and (b) were reasonable. (1 mark)

The purpose of part (c) is to train the students to think about the meaning of their work during the test. I do this check every time I do a problem on the board. Some students do this instinctively but I figured the mark for checking reasonableness would motivate the others, especially since they could earn full marks for the question even if (a) and (b) were wrong but part (c) was good. It was also an opportunity for a discussion about good test-taking skills.

I've had good laughs over students' answers before. And I got another laugh this time when a student got answers of 10^40 or more for each of parts (a) and (b) in m/s and s respectively. At the very least he conceded that 10^43 m/s was - and I quote - "an ungodly speed" and that it would take "several centuries" for MIR to orbit the Earth. Well, the universe has only existed for around 10^18 s. The laughs continued because I wrote "LOL" next to "ungodly." Well, the student thought that this was the greatest thing that any teacher had ever written. The camera phone was whipped out. Another fun answer: an orbital period of 0.3 s. Imagine three times a second: "There it goes... There it goes... There it goes."

Aside: I had another student use a camera phone to record a demonstration we did in class. It's a different world, eh? Interestingly, technically speaking, the students aren't even allowed to use cellphones in the school, let alone in classrooms. But clearly, there are great uses.

Keep reading... I have a second entry today.