Day 97 – Barbie Does Her Jump


Math 8 – Students did their Barbie Bungee Jump today. A few groups got really close!  The big difference between a good jump and not-so-good jump was that many students included the lenght of barbie in their equivalent ratio. So they not only multiplied the stretched elastic when scaling the distance but Barbie’s body length was multiplied too. This problem is avoided if graphing is used – Barbie becomes the y-intercept.  We may come back to this after linear relations.

Day 96 – Universal Gravitation

Physics 11 – And then there was the dreaded Universal Gravitation….  Why dreaded?  Despite my best efforts, students have a lot difficulties manipulating this equation. So many variables, so few numbers.  I generally find that students have a pretty fuzzy idea of algebraic manipulation.  They know some rules to follow (“if you have 4x, divide both sides by 4 to get rid of the 4”), but are pretty unclear on the mathematical underpinnings.  I looked at my son’s Math 9 textbook and I could see why this is the case.  I *think* that it would help to develop some understandings like: “the variable term will have a coefficient in front of it. Use the associative property to separate the coefficient and the variable, then multiple the term by the reciprocal of the coefficient so that the coefficient is 1.”

Other people may see the above as being too prescriptive or wordy, or not easily understood by students.  However, if a few of these steps are deliberately practiced, I would hope that the methodology would become clear and make sense.

Day 93 – Projectile Crime Scenes

Physics 11 – I pulled out an activity that I haven’t used for a few years, the ol’ Projectile Crime Scene.  Students are given one of three crime scenes to investigate.  Above you see the Hotel Jumper, where students use a scaled model/drawing of the hotel and where he landed.  The idea is that they will use the height to find fall time, and then horizontal distance and time to find the horizontal speed. From this, they use data tables on men walking and running speed to see if the man was pushed out of the window or if he ran and jumped in an attempt to land in a pool below.

The other two activities are very similar, they all involve a horizontal launch projectile where students need to find a horizontal speed.  These are engaging tasks but also very difficult because of the extra cognitive load placed on the students.  In the hotel jumper, the students need to deal with a scaled model.  In the Gangster Shooting, the problem involves a bit of math and reasoning to make a proper sketch of the crime scene. Road Rage involves some kinematics and acceleration prior to the projectile part.

Despite the difficulties, I believe it’s a good task to do. Perhaps it would be better if more practice was spent on projectiles. Or, despite it being a horizontal launch problem, it might be better suited to Physics 12.

Day 92 – Barbie Bungee Jump


Math 8 – The Barbie Bungee Jump is a really nice activity that works in so many different settings in secondary school. I’ve used it in Math 10 for graphing linear relations/functions, I’ve used it in Physics 11 as a graphing warm-up and modeling example, and this year we’re using it in Math 8 for ratios and rates. In a few weeks we’ll come back to it, and tie it in with linear relations.

I’m working on this with my teacher candidate.  Below is the handout that she developed and I tweaked (but just a little bit).

Math 8 Barbie Bungee Jump