Lego Mindstorm 1: Measuring Distance and Velocity

In this experiment, groups were asked to use the Lego cars to understand how to measure distance and velocity and also that through human error, these measurements may not always be perfectly accurate. The experiment was designed in a way such that the computer gave its measurement of distance traveled, which students could compare to the measurements they had taken themselves.

First, my partner and I measured the diameter of the wheel, which was necessary for us to find the circumference (pi*D) so that using the number of wheel turns, the computer could determine how far it traveled. We measured the wheel diameter at .055 m, so the circumference was .1728 m.

Then, we were asked to experiment with the power settings to see how far the car would travel. We experimented with three power settings, 75, 55, and 65, and performed three trials for each power setting to ensure that our data would be as accurate as possible. We kept our time at 1 second, both because our ruler was not very long and because it would make measuring velocity easy (velocity is measured in m/s, and if the distance is being measured over the time of 1 second, then the value for distance and velocity is the same).

 

This is the data we gathered on our very first trial:

Setting 1 (power=75) (time=1):

Trial 1, VI:  

    Rotation: 497 degrees

    Wheel Turns: 1.38056

    Distance: .238836 m

    Velocity: .238836 m

Trial 1, Student

    Distance .26 m

    Margin of Error: 8%

 

Through this data, some connections are clear. For example, the wheels rotated 497 degrees, which is just under 1.5 complete turns. The data shows that the wheels actually turned roughly 1.38 times. The wheel’s circumference was about .17 m, so it makes sense that the distance (according to the computer) was around 1.38 times that. All of this computer-generated data correlates. We were also asked to measure how far we thought the car traveled using a ruler, and each time we were slightly off. We used the difference between our measurement of distance and the computer’s measurement of distance to find the margin of error, which in this case was 8%. In some other cases the number was smaller (.614% which we were very proud of) but it was also larger in some trials (12.47% which we were less proud of). Our measurements were far from exact; we used a pen to try and align the ruler with the backs of the wheels, and our eyesight is not nearly as good at measuring as a computer is. We did constantly try to improve our exactness, but as is visible in the data below, this is a difficult thing to improve within such a short window of time. This experiment helped us to understand through hands-on learning how distance, wheel circumference, number of wheel turns, velocity, and timing were all related. Below you will find all of our data including the data I posted above:

 

Wheel Diameter= .055 m    Circumference= .1728 m

 

Setting 1 (power=75) (time=1):

Trial 1, VI:  

    Rotation: 497 degrees

    Wheel Turns: 1.38056

    Distance: .238836 m

    Velocity: .238836 m

Trial 1, Student

    Distance .26 m

    Margin of Error: 8%

 

Trial 2, VI:

    Rotation: 490 degrees

    Wheel Turns: 1.36111

    Distance: .2352 m

    Velocity: .2352 m/s

Trial 2, Student:

    Distance: .26m

        Margin of Error: .614%

 

    Trial 3, VI:

        Rotation: 488 degrees

        Wheel Turns: 1.35556

        Distance: .23424 m

        Velocity: .23424 m/s

    Trial 3, Student:

        Distance: .257 m

        Margin of Error: 9.266 %

 

Setting 2 (power=55) (time=1):

    Trial 1, VI:

        Rotation: 338 degrees

        Wheel Turns: .938889

        Distance: .16224 m

        Velocity: .16224 m/s

    Trial 1, Student:

        Distance: .184 m

        Margin of Error: .377%

   

   

 

Trial 2, VI:

        Rotation: 341 degrees

        Wheel Turns: .947222

        Distance: .16368 m

        Velocity: .16368 m/s

    Trial 2, Student:

        Distance: .182 m

        Margin of Error: 10.599%

 

    Trial 3, VI:

        Rotation: 342 degrees

        Wheel Turns: .95

        Distance: .16416 m

        Velocity: .16416 m/s

    Trial 3, Student:

        Distance: .186 m

        Margin of Error: 12.474%

 

Setting 3 (power=65) (time1):

    Trial 1, VI:

        Rotation: 419 degrees

        Wheel Turns: 1.16389

        Distance: .20112 m

        Velocity: .20112 m/s

    Trial 1, Student:

        Distance: .223 m

        Margin of Error: 10.318%

 

    Trial 2, VI:

        Rotation: 422 degrees

        Wheel Turns: 1.17222

        Distance: .20256 m

        Velocity: .20256 m/s

    Trial 2, Student:

        Distance: .22 m

        Margin of Error: 8.254%

 

    Trial 3, VI:

        Rotation: 427 degrees

        Wheel Turns: 1.18611

        Distance: .20496 m

        Velocity: .20496 m/s

    Trial 3, Student:

        Distance: .216 m

        Margin of Error: 5.245%