{"id":7218,"date":"2016-12-11T19:03:59","date_gmt":"2016-12-11T19:03:59","guid":{"rendered":"http:\/\/darngoodsolutions.com\/blogA\/?p=7218"},"modified":"2016-12-11T21:33:57","modified_gmt":"2016-12-11T21:33:57","slug":"tennis-ball-cannon-saga-shoot-first-and-ask-questions-later","status":"publish","type":"post","link":"http:\/\/darngoodsolutions.com\/blogA\/2016\/12\/11\/tennis-ball-cannon-saga-shoot-first-and-ask-questions-later\/","title":{"rendered":"Tennis Ball Cannon Saga – Shoot First and Ask Questions Later"},"content":{"rendered":"\n\n
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Science Teaching & Technology by Multimedia Science<\/em>
\nTennis Ball Cannon Saga
\nShoot First and Ask Questions Later<\/p>\n

\"1\"<\/a><\/p>\n

The Original Cannon<\/p>\n

After teaching physics and chemistry for several years, I attended a physics demonstration seminar.\u00a0 One physics teacher mentioned that he had built a cannon out of tin cans that would shoot a tennis ball and could be used as a demonstration of momentum.\u00a0 Thus began a twenty year process of building and rebuilding the tennis ball cannon which became one of the most effective and popular demonstration in my physics classes.<\/p>\n

Some research led me to the basic design which was to use several tin cans taped together attached to another can used as a firing chamber.\u00a0 A small hole was made in the firing chamber to both insert some propellant and to ignite it.<\/p>\n

In order to make the cannon into a demonstration for momentum, it had to be able to recoil.\u00a0 So I constructed my prototype cannons on momentum carts.\u00a0 Finding the right tin cans was quite a challenge.\u00a0 Some cans had such a tight fit around the tennis ball that the ball would not come out.\u00a0 The balls were so tight, that I had to disassemble the cannon to remove the ball.\u00a0 Other cans were so loose that, after ignition, the ball would literally just roll out the end of the cannon.<\/p>\n

\"download-2\"<\/a><\/p>\n

After many tries, I found the perfect sized can, which turned out to be small cans of V8 vegetable juice.\u00a0 The cannon was set up on a laboratory bench, the tennis ball was inserted, and casually I lit the propellant.\u00a0 BOOM!\u00a0 The tennis ball shot out of the cannon, bounced off of the wall across the classroom, and hit me right in the middle of my glasses (no lie).\u00a0 The cannon, meanwhile, recoiled, hit my hand, turned over, and hit floor.\u00a0 For the next several years, the physics cannon had a large dent in its firing chamber.\u00a0 Obviously, I had become careless after so many unsuccessful attempts.<\/p>\n

I devised a lab where the students were supposed to be government researchers investigating a new secret cannon.\u00a0 They had to use both momentum and projectile motion to calculate the velocity of the ball using two different methods.\u00a0 One student from each lab group were assigned to set up the firing range and the others worked on setting up the equations to calculate the two velocities.<\/p>\n

\"cannon\"<\/a><\/p>\n

After everything was set up, it was time to fire the cannon.\u00a0 Many of the students were not particularly impressed with the cannon.\u00a0 The propellant was added and the flame was set to the ignition hole.\u00a0 BOOM! The ball shot out of the cannon, hit the wall, and caromed back across the room. I saw that all of the student\u2019s eyes were now wide open and they began clamoring to do it again.\u00a0 I usually stood with the student whose job it was to catch the cannon, since the recoil was unexpected enough that they often missed.<\/p>\n

While there was some variation, the speed of the tennis ball often exceeded 100 miles per hour.\u00a0 All and all, it was the one demonstration \/ lab that students mentioned when they returned to visit after graduating.<\/p>\n

The New \u201cImproved\u201d Cannon II<\/p>\n

I continued to use the lone cannon for several years and soon other physics teachers began using it.\u00a0 Then one day I looked in the closet and the cannon was GONE!\u00a0 One of the teachers said that the cans had come apart so they had thrown it away.\u00a0 I was without my favorite toy that year and tried to recreate it without success.\u00a0 V8 juice was no longer sold in cans and the other cans I tried did not work.
\nHere is a YouTube video of an attempt to create a cannon using Pringles tubes<\/a> which had a few problems.<\/p>\n