PhET + Speeding in Compton

Ever get that feeling that you’re squeezing every part out of a class (aka I’m likely trying to cram to much in…)? Teaching a 90 minute block gives me a lot of time and we can sign up for a computer lab in 45 minute segments. Class started off in the lab looking at a motion simulation from PhET.

The Moving Man

My students have experimented with a few of the PhET simulations through the year and have enjoyed moving at their own pace and being able to go back whenever they want. In this case, students could move the man and see the correlation between position vs time and velocity vs time graphs. If you haven’t visited the PhET site, check it out as there is a variety of simulations.

Returning to class, students were given this video clip and the question of “Should this person be given a speeding ticket?”

Yep, it’s an oldie from Dan Meyer. Groups had a few moments to put together questions. A few include…

  • What happens when the blue dot stops?
  • What is the speeding limit? (Dan has an image of a speed limit sign.)
  • How long is the dot moving? (A second video includes a timer.)
  • What is the distance?

With the last question, I decided to  give them intersection information – West Slauson Avenue @ Crenshaw , Los Angeles. I’ve done this problem before with giving students a block length but I wanted to see if students would check out a map. As it turned out, this part of the problem was the stumbling point. Even with hints to use the laptops carried by many students, the address information stayed unused.

As another hint, I posted this image:

Many students ran to the board with a meter stick to get data off while one yelped “Ooh” and quickly opened her laptop. The clock was ticking to the end of the class and the room was quite a-buzz with students trying to determine how fast the little blue dot was moving across the screen. At the same time, many still did not have a good handle on the distance traveled. The final image –

The groups still wondering about a distance could find the information they needed and as the class wound up we went around to groups to decide whether or not a speeding ticket was necessary. The first group – “No”. The next few groups decided that the driver should get a ticket and go to jail with speeds over 100 mph.

It seems as if many students are still OK with whatever number comes out of their calculation cruncher. I realize that they are not drivers but the big number did not raise many alarms. Could someone be driving that fast? Ambulances, police car chases and crazy drivers came up as possibilities. Another student, trying to be funny, said that maybe it is just an airplane. Hmmm……


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