General -- Problem Set #1

Question #6 -- The Magnus Effect

Here is the actual experiment, recorded as a movie and also as still frames.

Hoping you enjoy!

Extra Hint for Solving:

Differential equations are an awfully important part of figuring out problems in science. And pretty interesting in themselves. Useful, pretty -- worth having a look at.

If you've done any integration, and a little differentiation, you can get somewhere with differential equations. POPTOR has prepared a little briefing on differential equations to help you solve our problems a little more easily. Have a look at Brian Mullins's Guide in PDF format or on the webpage in GIF format.

Solutions and Marking: Comments & Feedback

I'll say that overall we're pleased with how people did on the first set. It was different, it was pretty hard, but people did some pretty intelligent things. It was a set composed for bright students looking for a special challenge, so even to participate will have put you into a special category of student!

Here's some specific feedback. As is usual for POPTOR, few students attempted all questions. Below I give what the average was for each question, including for students who gave no answer, and also the average just for the students who attempted the question. Not surprisingly, the average among students who attempted the question was significantly higher!

I hope people will feel free to attempt questions they don't know how to solve well. We sometimes give marks just for a good sketch of how one might approach the problem, given more time, computing power, etc. So please don't be too shy, given so little to lose...

Question 1: The path of least resistance
Total of marks 246
Overall Average 3.3
The number of students attempting question is 58
The average of those who attempted is 4.2

Question 2: The last straw
Total of marks 269
Overall Average 3.6
The number of students attempting question is 46
The average of those who attempted is 5.8

Comments

This question was done quite well with the majority of students getting
8's, 9's and 10's.

Question 3: Fermi, fer you
Total of marks 300
Overall Average 4.0
The number of students attempting question is 61
The average of those who attempted is 4.9

Question 4: Number four with a bullet
Total of marks 217
Overall Average 2.9
The number of students attempting question is 44
The average of those who attempted is 4.9

Comments:
Of the people who attempted this tough question roughly half got the physics
totally right and half missed the mark. Of the people who got the physics
right, about three quarters were able to work the algebra and complete the
question.

Question 5: Bubbling Ideas
Total of marks 94
Overall Average 1.3
The number of students attempting question is 32
The average of those who attempted is 2.9

Question 6: Magnus matters
Total of marks 102
Overall Average 1.4
The number of students attempting question is 22
The average of those who attempted is 4.6

Comments:

Not many people attempted this question. Of the students who did do the
question most got only 2's, 3's and 4's. Most of the marks were lost on
the experiment part as the students didn't show raw data and just stated
their conclusions.

Last revised: 2 February 2001 -- rsm