As we approach the coming of Fall Finals, you may find yourself with a little extra class time on your hands. Maybe one of your sections is ahead of the rest, maybe you have an early dismissal looming, maybe you have a ton of kids who are exempting your final. Watching movies may or may not be frowned upon where you are, or you are short on something they would enjoy watching. I humbly suggest Straw-based engineering challenges. It's extremely successful every time I do it, and there are tons of ways to mix up the rules. Only rarely will you find a group unwilling to do it or fall flat on their face.

Long ago when I was in AP Physics, we took a field trip to a university on a Saturday. They were holding a design competition and they were giving away scholarships for the winners. We had no idea what to expect and hey, who doesn't like field trips? The contest was to build a straw tower that optimized various categories (weight, height, etc) and could support a tennis ball for a certain amount of time. This project is extremely similar to the popular marshmallow tower challenge. I have done the marshmallow challenge at times, though it can get a little messy, and sometimes I have more than 15 minutes to kill.

Over four years, I have presented the task in a number of different ways:

Version 1

50 full length straws

1m of tape

Build Time: 2 hours

build the tallest structure that supports a tennis ball for 60s

Version 2

50 full length straws

1m of tape

Build Time: 1.5 hours

build a structure at least 18in tall that supports a tennis ball for 60s

Version 3

30 full length straws

1m of tape

Build Time: 1 hour

build a structure at least 18in tall that supports a tennis ball for 30s

Version 4

30 short straws (~3", coffee stirrers that are a tad thicker than usual, found a box of 1000 for $4 at Office Depot)

1m of tape

Build Time: 25 minutes

build the tallest struture you can that supports a tennis ball for 60s

Version 5

45 short straws

1m of tape

plastic bag

Build Time: 25 minutes

build a structure that supports a tennis ball within a defined volume but no straws may touch the table inside that volume

This year I did Version 4 with an Algebra II class and Version 5 with my Pre Cal students. Version 5 is the most recent and one of the more interesting variations. The official instructions were they could use only what I gave them, and they could mutilate the straws in any way they wanted. If they asked to use the bag, I let them use the bag. Of the three class periods that did this version, one did not ask about the bag. The "no straw zone" was a 1ft x 3in area marked on their tables. No straws could sit on the table in this area. I did not set a minimum table clearance and probably will in the future. I did not forbid them from taping straws to the table and probably will ban the practice in the future.

Some results:

strawalg1.jpg
strawalg2.jpg
straw1.jpg
straw2.jpg
straw3.jpg
straw4.jpg
straw5.jpg
straw6.jpg

This last one year in particular got me thinking that I should've set a height clearance, but kudos to them for exploring the boundaries of the rules. Also a big hats off to the group that had the genius idea of situating the tennis ball inside the bag. Again, a minimum height clearance would've made that strategy more challenging to implement, but bravo to them.

My favorite part is how tense they get when it's time to test their structure. It doesn't matter if they finished early and have had the ball sitting there calmly for minutes on end. Somewhere deep down they're afraid the structure will explode when they're on the clock. It's hilarious.

Posted
AuthorJonathan Claydon