Linear velocity

The morning session began with notes on the laboratory reports and a demonstration of the options in Desmos using the graph from the density lab.

Then I introduced the topic asking what shape would occur on a time versus distance graph for an object moving at a constant speed. This drew no responses. None. 

I eventually suggested that a smiley face was possible. And when one student thought s smiley face was not possible, I went ahead and made a crude representation of one on the density graph which was still up on the Smartboard. I made the point that even a smiley face can be built from mathematical models, mathematical equations. And that Desmos makes these equations accessible such that even a 13 year old student can create art with Desmos and mathematical equations. I tried to draw the distinction between math as taught in school which focuses on solutions to equations to the ability to think mathematically. Solving equations does not produce mathematical literacy. None of my students had a clue as to how to make a smiley face in Desmos. And yet... the 13 year olds. 

Following this I covered how to use the stopwatches using a sketch on the board seen further above.

On the sidewalk I did a 30 meter RipStik run. 

The run came in at 1.75 m/s. 

The laboratory session began with rolls from west to east. There was only a light breeze, but this was enough to make eastbound runs problematic. I then reversed direction and rolled westbound runs. These went much better than the eastbound runs. This surprised me because the wind was very light and variable. 

I again reused the three meter intervals from the morning for the slow and medium speed balls. 

I shifted to 6 meter intervals for the fast run. The slow ball runs came in at around two meters per second. Any slower and the ball drifts to a stop or rolls off the course prematurely. The medium runs were up around 3.8 m/s. The fast ball runs were more variable. One of the runs was 6.9 m/s. These are not the all out max velocity of the old five meter interval days, these are more controlled and slower. Timing is easier when the fast run is actually slightly slower, more controlled, and timed on a six meter interval.  

Friday included coverage of slope equals zero and the impossible/undefined vertical line on a time versus distance graph.

Friday wrapped up with a demonstration of the Bernoulli theorem using two inch wide strips of copy paper and the Magnus effect using only table tennis balls and a scoop ball thrower/catcher. Sandpaper in the scoop ensures that the table tennis ball gets a solid spin to demonstrate the Magnus effect.