10 Days of Science with Math: More on Calculating Velocity


Here is the repost of our Finding Velocity results. This was a great lesson and it spawned two more activities using the LEGO Mindstorms nxt brick. E had to make a marble speed trap using the light sensor and a while later he made a speed trap using the ultrasonic sensor. The update there is that he was successful in measuring the speed of a large ball coming toward the robot- it needed an object bigger than a marble.

young teen sitting in front of a bookshelf smiling at the camera with a title overlay that says, science with math: calculating velocity
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two kids dressed in clean room suits putting a marble down a very tall hand built marble run

Here is the much anticipated result of our marble investigation. I was delinquent in getting pictures to go with my results. I have to have the pictures! If you missed the first post on our most excellent math lesson, then go to there and read about it. It was good science!!

The first thing the kids found was that it was hard to get the marble to repeat a good run enough times to record it for five trials in a row. They tried to get the marble to go around the curve correctly each time to no avail. Finally, they ended up making a new chart to record the partial runs. We could calculate the velocity whether or not the marble went all the way to the end of the track.

  • The data chart-we recorded the time in seconds using a kitchen timer. Each of them took a turn helping to hold up the part of the track near the curve, timing, and letting the marble go.
  • Then we measured the length of the track at both the partial and final marks
  • and I marked the yarn with the start and partial distance. That was important later on.
  • E11 used a yard stick to record the full and partial length of the track.
  • Then we had the mathematical task of converting the measurement to inches.

Then I thought I’d give E11 the challenge of converting our answer from inches per second to miles per hour. That was fun! Yeah…I’m that kind of mom!

Some things to think about- first the kids wanted to give up on the full track runs, but I made them stick with it. E11 was especially annoyed and declared it was all ruined several times, but I reminded him about how scientists meet up with obstacles all the time. Dan, my husband, helps to manage a university lab (and now is a director of a lab facility) full of users who get frustrated the same way. Months of work will come to a crashing halt when they make a mistake or a tool is dirty and ruins a wafer or a tool is broken and breaks something they’ve worked hard on for a long time.

Besides, E11 is a very bright boy who needs to work on perseverance when something is more difficult than he would like to battle.

Also, before we could do calculations, we had to deal with the raw data. We chose to find the median rather than an average in order to do the velocity calculation.

We had trouble importing the video from E11’s camera into Picasa so for now the video of the run will wait. Next time… Aha! E11 just informed me that his camera card was not wiped so perhaps, with my help, we’ll load up some video for you. That was part of the challenge that day.

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