Ballistix Chair!

Do you have one of those little ballistics carts that shoots a steel ball straight up into the air while it rolls and the ball comes right back down into the "barrel" later? Showing independence of horizontal and vertical motion in 2-D? Yeah? So do I. THREE of them. Don't use them anymore.

I've found a few problems with these over the years.

1. I lose the caulder pins so I have to make a new one or go buy one - and neither one ever fits right again!
2. I lose the whole dern cart!
   
3. The carts cost a whopping $77.00 EACH! Golly, for that I could hang out at my favorite WaWa for a WEEK!
4. The barrel mechanism gets a little rusty and/or a little crooked from falling off the demo desk during demos it was never designed for and the "pull back" of the caulder pin slows the cart too much and the demo doesn't work and the kid's all yell, "Ha Ha! You lied to us again, Mr. Taylor"! And my self-esteem is shattered and I get dismissed after a bout of heavy chocolate milk drinking and end up selling pencils on the street after my family leaves me and... Oh, never mind... I'm back now...

So, since I don't want that to happen to you, here's a moldy oldy to demonstrate 2-D independence. I used to do this one back in my Delran days in the '80's. Other teachers thought I was wack-o for pushing kids down the hallway on desk chairs. I had forgotten all about this one till, just today, in my very own classroom, I saw Miss Justine Ruth, Justine's PhySci WebSite or email Justine, a rising star in science teaching, doing it as a demo for her 9th graders... Keep note of that name - she's gonna be a teaching star someday.

Anyway, what do you need for this complex demo?

1. A chair with wheels. A nice leather executive chair borrowed from the Principal's office works just fine. (Remember, DON'T ASK! It's easier to ask for forgiveness than for permission...)
2. A ball to toss. Tennis balls seem to be the kid's favorite. They don't seem to like my bowling balls for this one. Can't fathom why.
3. A kid to sit and toss, a kid to push, and a kid to observe.

PROCEDURE:

1. Partner 'A' sits in specially designed Ballistix chair.
2. While stationary, 'A' will practice throwing a ball straight up and catching it. Keep practicing till 'A' can toss and catch consistently with EYES CLOSED.
3. Partner 'B' will now push the specially designed Ballistix Chair at a constant speed.
4. 'A' will throw the ball STRAIGHT up into the air with EYES CLOSED.
5. Partner 'C' will observe the path of the ball and record the observations.
6. EACH partner, A, B, & C, will do the throwing in turn so EACH partner will observe another.

Now, to add a little spice to this demo, have a "volunteer" demonstrate this using a SuperSoaker water gun! Have the kid shoot a short burst of water straight up as he is being pushed. The water will invariably come down on the kid's head - IF the speed is low enough so that air resistance doesn't enter into it...
SAFETY NOTE: Don't use a high-powered watergun inside your regular classroom. I found out that ceiling tiles don't like large gusshes of water... Ah, the powers of foresite...

Basic observations should include the path is parabolic AND Partner 'A' can normally catch the ball even tho he/she NEVER gave t a horizontal push. Same effect as the $77.00 Ballistic Cart and it's free and kid's have fun while doing it. Can't ask for anything more, can you?