SL2RL-Math247

22 February 2009

Goodie of the Month – Fun and Learning with Quadratics

Filed under: applets,education,ICT,math — Tags: , , , , , — admin @ 3:23 am

Goodie: “A technique/question that can be applied in many places and teaches thinking.”

Baddie: “A technique/question that is a waste of good teaching and learning-to-think-and-do-math time.”


February 2009 Goodie of the MonthReal Fun and Learning with Quadratics

In the second half of Algebra 1:

A typical standard is: Apply quadratic equations to physical problems, such as the motion of an object under the force of gravity.

A typical question for this is: A ball is thrown straight down with a speed of 20 [ft/s] from a height of 80 [ft]. When will it hit the ground?

A typical application of technology is:

Tell the student that the function is y(t)=-16t2-20t+80. They know they can’t graph with t so they switch to x, which they graph on their graphing calculator.

They see that parabola crosses the x-axis. They find the intersection and write x=1.7 and get their points.

Now ask them "Where does the ball hit the ground?". They will point to the intersection point – totally forgetting that this is vertical motion and that the ball hits the ground at (0,0)!

Ask them "What is the units on your answer?". You will be lucky if they give you [seconds] and not [feet]!


So why is this a “Goodie of the Month”?

The problem isn’t the standard. Nor is it the question. Both are excellent. The problem is the technology – it is undoing the learning.

Let’s change the technology!  If the animation below doesn’t work – open this link: Vertical Motion


 

 

 

 

 

 

 

 

Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser (Click here to install Java now)

Here are some “good problems”.

  • Set ho = 80[ft] and vo = -20[ft/s]. Run the animation. Point with your finger to the place where the ball hit the ground. Now find the place on the graph where it says when it hit the ground.
  • Set ho = 80[ft] and vo= 20[ft/s]. Run the animation. Notice that the ball goes up before it goes down. Why is this? Reset the animation and using the step forward + and step backward – buttons, stop the animation when the ball is at its highest point. Point with your finger to the place where the ball is at its highest point. Now find the place on the graph where it says when it is at its peak. What time is this?
  • Set ho = 0[ft] and vo= 100[ft/s]. Find when the ball hits the ground. Do this via the animation and algebraically using the function. When is the ball at its highest point (remember – parabolas are symmetric!)? What is this highest point? Do not forget units!

Here are some “good questions” for the function: h(t)=ho+vot-16t2

  • The function h(t) gives height in [ft]. So each member of this function must give [ft].

    • ho is (initial) height. So its unit is [ft]. It is all by itself so this member is in [ft].
    • vo is (initial) velocity. So its unit is [ft/s]. How does this member give [ft]?
    • What do you think the unit of “16” is so that this last member gives [ft]?
  • In what part of the function is gravity playing a part? In which of the above problems is the only force gravity?
  • Why do you think there is a plus sign in front of vo and a minus sign in front of 16? That is, what does it mean in mathematics/physics for an object to have a positive velocity? Does gravity increase this velocity?
  • Make up a problem that describes this situation: ho = 0[ft] and vo= 100[ft/s].

Links for this interActivity (worksheets, downloads, etc.): Open Metadata

25 January 2009

Goodie of the Month – A Good Question for Algebra 1

Filed under: algebra,applets,education,ICT,math — Tags: , , , , — admin @ 2:01 am

Goodie: “A technique/question that can be applied in many places and teaches thinking.”

Baddie: “A technique/question that is a waste of good teaching and learning-to-think-and-do-math time.”


January 2009 Goodie of the MonthA Good Question for Algebra 1

Two ships are sailing in the fog and are being monitored by tracing equipment. As they come into the observer’s rectangular radar screen, one ship, the Rusty Tube, is at a point 900 mm to the right of the bottom left corner of the radar screen along the lower edge. The other ship, the Bucket of Bolts, is located at a point 100 mm above the lower left corner of that screen. One minute later, both ships’ positions have changed. The Rusty Tube has moved to a position on the screen 3 mm left and 2 mm above its previous position on the radar screen. Meanwhile, the Bucket of Bolts has moved to a position 4 mm right and 1 mm above its previous location on that screen.
Assume that both ships continue to move at a constant speed on their respective linear courses. Using graphs and equations, find out if the two ship will collide.

Why do I like this question?

  • Students can understand it and it is fun.
  • They can graph it on paper or using a graphing program.
  • It involves finding the equation of a line through 2 points (twice) – good reinforcement.

Why do I think it is a “good question”?

  1. The graph looks like every 2×2 system of linear equations they have solved in Algebra 1.
    • It looks like the boats collide at the intersection point (see below).
    • It seems like all they need to do is solve the system and be done.
    • … until you say “Where is time on the graph?”.
  2. The student can build a animated simulator that “shows time” – easily!
  3. The kids can make the boats collide – what fun!.
    • They can move the starting points until they get the boats to collide.
    • They can also adapt the simulator so that they can change the slopes and get the boats to collide. Directions here.
    • My thanks to David Cox for seeing this!
  4. You can get all kinds of mathematics out of them.
    • You can get them to calculate when each of the boats reaches the intersection point in the original question.
    • You can get them to check the math on their “colliding simulator” to see if the boats really do collide, where and when.
    • You can ask them about a 3D graph and what this would look like when the boats don’t collide and when they do.

To animate, click on the play button at bottom left of graph.

To animate manually, right-click on slider and deselect “Animation on”. Then, click and drag the point on the slider.

Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser (Click here to install Java now)

Source: I found this question asked on answers.yahoo.com. My webpage for this question is: mathcasts.org/mtwiki/Gq/BoatCollide

2 January 2008

Facts+Skills+Thinking: Applets and the Vitruvian Learner

Filed under: applets,education,ICT,math — Tags: , , , , — admin @ 12:44 am

We want our learners to know facts, to have skills and to be able to think – a perfectly proportioned Vitruvian Learner.

I am preparing a new course on ICT* in Education. Most of the literature on this is depressing – no kidding. Everyone is still so enthusiastic about the future of ICT in education, but most admit that current ICT integration has brought no significant breakthroughs in student learning. ARGH!

At the same time, I was just designing a set of math applets** for measuring angles with a protractor (link). This turns out to be an exercise for which there are many, many, many such programs available. ARGH!

Of course, I think my applets are different – they will bring the breakthroughs. But why should they? For the moment, let’s assume that magically my applets are loved and are being used in every classroom in the land …

What about these applets might bring a breakthrough in student learning?

To be effective:

The applet must be a perfect proportion of facts, skills and logical thinking processes both required to use and acquired from use and

• this required perfect proportion must apply to a large number of learners.

• this acquired perfect proportion must apply to a large number of curriculum.

One easy conclusion – the smaller and more focused the application – the better chance it has of meeting these requirements. Hence, applets and not mega applications probably are more practical.

Even more essential is communication with teachers because a teacher will not use ICT unless it can be used within the curriculum, i.e. within the framework of “this is what we know so far and this is our goal in this lesson”.

So – just from the point of view of bringing a breakthrough in learning – and before designing an applet, we must ask.

• What are the facts one needs to know to use and what facts will be learned?

• What are the skills one needs to know to use and what skills will be learned?

• What types of logical thinking process are required? What thinking processes will be learned?

Then: Do these answers fit a broad spectrum of learners and curriculum?

Yes? On to the next checklist …


* ICT: Information and Communication Technology, sometimes just IT.

** applet: A little application frequently run from a browser window with limited features that requires limited memory resources.


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