- 1.5" PVC pipe (Jon uses an 8 ft pipe, but shorter is ok) (clear tube if you can afford it)
- 1/2" drill bit (to make a hole drilled about 2" from one end of the PVC pipe)
- 3/8" hose barb (something like this, may need different size depending on vacuum tubing)
- Teflon tape (wrapped around barb before it is screwed into 1/2" opening in pipe)
- 40 mm Competition Ping Pong Ball (as we saw, the basic/cheap ones won't work)
- 3" 3M 375 clear packing tape
- Jon also mentioned you may need a coupler on each end for added surface area
- Soda can (with a book on top for added inertia)
Here is the result of trial 1:
Here is the result of Trial 2:
The yellow you see is the ping pong ball that broke through the front side of the can. As I mentioned, Jon's 8' howitzer cannon can shoot through 2 cans. He said he saw that the one made at U of Minnesota can go through 3. Let the carnage begin!
this demo is aweomse, and it's a great way to get a very rough lower bound on the speed of air molecules—they have to be moving faster than the ping pong ball when it leaves the cannon.
ReplyDeleteSomeone suggested to me that I replace the packing tape with mylar held in place with a coupler. You can use either scraps for old mylar balloons or I believe he used potato chip bags. This change made a huge difference! We captured a high-speed video of it in action: http://pedagoguepadawan.net/28/halloweenphysics/
ReplyDeleteGeoff,
ReplyDeleteThanks for the info to make the launcher even better!