[MWForum](Fwd) Trying to write a procedure for a football kickoff

[Ray Catzel]

Hi Daniel,
That is a nice intuitive solution to the kicking problem. I had once used a
parabolic formula to describe the motion path (typical of balls and
missiles); however your method is far better for students to understand. I
like the arbitrary but effective way you incorporate gravity.
-----ray

-----Original Message-----
From: mwforum-admin@lists.mathcats.com
[mailto:mwforum-admin@lists.mathcats.com]On Behalf Of Daniel Ajoy
Sent: Thursday, December 04, 2003 8:34 AM
To: mwforum@lists.mathcats.com; RATZEL, MARSHA; Ian Bicking
Subject: [MWForum](Fwd) Trying to write a procedure for a football
kickoff


Hi Marsha,

I used Ian's idea to create the attached project. I hope it helps
you understand what he was talking about.

Daniel
OpenWorld Learning

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   Date: Wed, 3 Dec 2003 11:25:00 -0600
   From: "RATZEL, MARSHA" <MRATZEL@bv229.k12.ks.us>
Subject: Trying to write a procedure for a football kickoff

Such heady conversation makes me a wee timid to ask such a basic
question, but I've got a problem and I'm stumped.  I've been helping my
students work on their animations.  They are so thrilled and pushing me
to learn more and more each day...so I'm way beyond my ability.  Which
is the whole point of this co-journeying isn't it.

I have several students who want their animations to do things like kick
a football or bump a volleyball over a net.  Now I totally understand
that I could create a nonlinear function that I am guessing I could
include in a procedure that would accomplish that task.  But my 7th
graders don't know about nonlinear functions yet.  They do know about
creating x and y tables that have coordinates which record the path that
those balls would take....but they don't yet know how to write the
"rule" that describes how the x relates to the y.

So I am asking for advice on how to help them write their procedures to
accomplish their animations.  Is there a way to do this?  I've tried
thinking about using some variation of repeating fd and rt and then
changing at the top to fd and lt .  We've not had much success with
that.  And I don't understand enough about seth to know how to do that
either...but am wondering if that's the way I should go.

Can anyone help me with my very basic understanding of MW 2.0 and my 7th
graders?  I'd appreciate your help and they would be so thrilled with
their projects.  Thanks.

marsha

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   Date: Wed, 3 Dec 2003 15:40:54 -0600
   From: Ian Bicking <ianb@colorstudy.com>
Subject: Re: Trying to write a procedure for a football kickoff

On Dec 3, 2003, at 11:25 AM, RATZEL, MARSHA wrote:
> Such heady conversation makes me a wee timid to ask such a basic
> question, but I've got a problem and I'm stumped.  I've been helping
> my students work on their animations.  They are so thrilled and
> pushing me to learn more and more each day...so I'm way beyond my
> ability.  Which is the whole point of this co-journeying isn't it. 

This is an entirely appropriate question for this forum.  If we talk
about language design and that stuff, anyone should feel free to simply
ignore that if they want to, and these sorts of questions remain just
as on-topic.

Which is mostly why I'm responding, but I'm not sure about the answer
to your question.  But I'll try... ;)

> I have several students who want their animations to do things like
> kick a football or bump a volleyball over a net.  Now I totally
> understand that I could create a nonlinear function that I am guessing
> I could include in a procedure that would accomplish that task.  But
> my 7th graders don't know about nonlinear functions yet.  They do know
> about creating x and y tables that have coordinates which record the
> path that those balls would take....but they don't yet know how to
> write the "rule" that describes how the x relates to the y. 
>  
> So I am asking for advice on how to help them write their procedures
> to accomplish their animations.  Is there a way to do this?  I've
> tried thinking about using some variation of repeating fd and rt and
> then changing at the top to fd and lt .  We've not had much success
> with that.  And I don't understand enough about seth to know how to do
> that either...but am wondering if that's the way I should go. 

Since you are modeling physics, I think it would be appropriate to use
natural physics equations here.

In that model X and Y are separate -- the Y is controlled by gravity,
while X stays the same (as the ball keeps the same forward velocity).
To avoid complicated equations, you should just start off with a X
speed and a Y speed (I'll call them :XSPEED and :YSPEED).  And we'll
make up a number that represents "gravity", :GRAVITY.    And so it
doesn't go forever, we'll stop the procedure once the ball falls below
:MINY (ground level).  Then use XCOR, YCOR, and SETXY to do the
function:

TO KICK :XSPEED :YSPEED :GRAVITY :MINY
   WHILE [YCOR > :MINY] [
     SETX XCOR + :XSPEED ; move ahead by :XSPEED
     SETY YCOR + :YSPEED ; move ahead by :YSPEED
     MAKE "YSPEED :YSPEED - :GRAVITY ; decrease :YSPEED each time
   ]
END

I'm not familiar with MW, so I'm not sure if it's called XCOR, POSX, or
something else, but it's intended to get the X position of the turtle.

This is a great lesson in physics and trajectories as well -- maybe if
you teach them SETX/SETY and XCOR/YCOR you can guide them to come up
with this procedure on their own.

--
Ian Bicking | ianb@colorstudy.com | http://blog.ianbicking.org

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