Unrelated to St. Valentine, here are some pictures from an awesome cannon-shooting outing today.
I had to build a little launching pad in order for it to stand straight up (to try to get it to travel directly upwards).
Here's me, setting up (wearing goggles because people told me that the cannon might blow up randomly upon multiple uses). I told the kids to stand way back.
Here my kids are measuring their horizontal distances away from the launch pad. (Making the rough assumption that the cannon's going to shoot straight up.)
The girls are getting ready with their inclinometers to catch the action! (Notice that there was quite a bit of wind today. That might have contributed to the cannon shooting a bit crookedly.)
And... (drum roll, please) Here is a video. (Notice that I was no longer lighting the cannon by this round. I took a volunteer but I told her that there were some risks involved.) This wasn't our best attempt from a logistical standpoint, since the cannon shot the ball out crookedly and made it hard for the kids to get an accurate angle. But, afterwards I estimated the hang time using the video, and found that it was ~5 seconds -- which, if you use the equation H(t) = -4.9(t - 0)(t - 5), you get a max height of ~30 meters!! WOW.
(The highest straight launches they were able to measure were about 20 meters, so this one went quite a bit further. It was also a bit later in the day, so more of the ethanol must have vaporized into the cannon before the launch. But, anyway, according to the kids, it definitely went "mas lejos!" than the previous attempts.)
PS. Did you know that Obama is coming to El Salvador, and that we get gratuitous days off because they're blocking off parts of streets around the school? I can't believe it; never heard of anything like this before.
Wow! Do you have instructions for this activity?
ReplyDeletehttp://untilnextstop.blogspot.com/2011/02/trig-love.html has a word file at the bottom that has a blueprint for how to build the cannon and the projectile. When you fire it, you squirt a very small amount (~2 droppers) of 95% ethanol inside the chamber (squirt them onto the inner walls of the chamber) and you close/seal the chamber and wait a couple of minutes for it to vaporize inside the chamber. Light with a match at the small hole at the bottom.
ReplyDeleteIf you do multiple rounds of firing, you have to open it up in between rounds to let air in for the combustion to happen.