 # Need helps to develop a lesson plan about the speed of a falling object

Hi, this is Mika Tanaka from Japan.
I am teaching junior high school students.

I have several questions for developing a lesson plan about measuring the speed of a falling object with Sphero BOLT.

The final goal of my lesson is that my student will be able to calculate the speed of a falling object from 50 meters.

In my lesson plan, my students will drop Sphero from each distances, 0.5, 1, 1.5 meters.
Then they will get the sensor data and CVS to find the speed numerically.
After that, they will create a graph about the relationship of the distance and the speed. ( the graph supposes to be in direct proportion between these two variables.)
When the graph is completed, they will try to calculate the speed of falling a abject from 50 meters.

I tried this procedures by myself, but I found several problems.

When I provided the CVS to check the result numerically, it showed not really precise results.
I think it is because Sphero BOLT measeures the speed with only X axis and Y axis.

Is there any great way to make my lesson plan possible?

Best Regards,

Mika Tanaka

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Hi Mika!

I’ve reached out to one of our engineers for some guidance on your question, and this was his response:

In order to calculate the speed of a falling object, you can’t use the X Y speed of Sphero.
That speed is entirely based on the encoders in the robot, so the robot needs to be moving its wheels in order for us to take a measurement.
For your specific example, the way to go would be to use the accelerometer data, and integrate it over time. The problem here is that the sensor streaming gives you 10 data samples per second, which is not a ton for the experiment. Then, you have to subtract gravity from the data points, since the sensor shows 0g when free falling.

So it sounds like what you are looking for is possible, but your initial conclusion was correct about the X & Y speeds.So, it would require some additional supports to make it work as you described.

I’d love to see what you put together, so you should share what you create here!

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Thank you very much for your help!

If it works well, I will post my lesson plan here to share.

Once again, I really appreciate your reply! Mika Tanaka

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