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Constant Speed Buggy ? How constant ?

Presenter:  Andy Jackson Harrisonburg City Public Schools,


Va. SOL:
PH. 1 The student will plan and conduct investigations using experimental design and product design processes. Key concepts include
    the components of a system are defined;
    instruments are selected and used to extend observations and measurements;
    information is recorded and presented in an organized format;
    the limitations of the experimental apparatus and design are recognized;
    the limitations of measured quantities are recognized through the appropriate use of significant figures or error ranges;
    models and simulations are used to visualize and explain phenomena, to make predictions from hypotheses, and to interpret data; and
    appropriate technology, including computers, graphing calculators, and probeware, is used for gathering and analyzing data and communicating results.
PH.5 The student will investigate and understand the interrelationships among mass, distance, force, and time through mathematical and experimental processes. Key concepts include
    linear motion




This lab focuses on three aspects of physics; experiment design, an understanding of constant speed, communicating findings to a larger group.


  • Constant speed buggy
  • meter sticks
  • stop watches

Image from Accessed on December 20, 2010.


Safety Considerations


Long hair should be secured back so it can not become entangled in the buggies drive wheels.



The lab above represents another step I’ve taken to allow the student to have more control of his/her own learning. A step towards more of an inquiry style lab and a step away from cook book style labs.  I conducted this lab on day three of my course. The only instruction the students have had at this point is a lab reviewing measurement and significant figures, and a lab regarding experiment design.

The students began playing with the equipment and discussing how they were going to conduct the experiment. There were five groups of four students in the room. After a little bit of time (maybe five minutes) I noticed that four of the five groups were using the same approach. They had marked off a measured distance and would put the cart at the start and time how long it took the cart to complete the distance. They would then record the time and repeat. The working assumption seemed to be that if the cart completed the given distance in the same amount of time over and over, then it was traveling at a constant speed. I interrupted their work to provide the following example: “If a runner completes the 100 m dash consistently in 12.0 s, does that mean he runs at a constant speed the whole time?” This seemed to instantly click with all the students and all groups immediately broke their distance down into intervals which they timed.

When the students reported their results to each other, some groups had calculated speeds by dividing the distance interval by the time interval while others just reported the amount of time needed to move through equal distance intervals. Most groups identified any variance as proof that the cart did NOT have a constant speed and were ready to sue for false advertising. This led to a useful conversation about measurement uncertainty that was NOT expressed by the significant figures. For example the stopwatches displayed times down to the hundredth of a second, but the students quickly agreed that their procedure did not allow for that degree of precision.  The end product was that all groups were able to express the average speed of the cart and provide a bracketed range for that speed. A common form for communicating this was “23 cm/s ranging from 20 cm/s to 27 cm/s” where the groups often cited the extremes of speed they measured as being the limits of the range.  At the conclusion of the presentations to each other there was still debate about if the carts truly had a constant speed or not. I do love a good physics argument.


Constant Speed Buggy ? How Constant?


There is more to life than increasing its speed.
Mahatma Gandhi
…then Gandhi would’ve loved this lab!

Simple Problem: The cart provided is advertised as a constant speed cart. What is the constant speed of the cart, and how constant is it?

Materials: stop watch, meter stick, constant speed cart

Procedure: Develop and write up a procedure that will allow you to answer the simple problem.

Data & Results: Make sure you record measurements in a way that you can use to convey your information to other lab groups. Record them on paper and put them on a white board.

Conclusions: Answer the question of the simple problem both on paper and on your whiteboard to present to other groups. Include any additional questions your work may have made you think of.



Sources and References


Buggies are available form The Physics ToolBox for $6 each (Click here)

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