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Science Fair Guide: Roller Coaster


In addition to the roller coaster materials, you’ll need a stopwatch and a heavy object.

Ask a Question

What type of slope will accelerate the marble the fastest?

Gather Information

The marble relies on the force of gravity to speed it up as it travels down the track. A steeper slope will accelerate the marble the faster, however the total track length will be longer. A perfectly straight slope will be the shortest distance between the start point and the end point, however it won’t be very seep, so the marble won’t accelerate very quickly.

To accelerate the marble the fastest, there needs to be a balance of steepness and total track length.

For further information, research the Brachistochrone problem.

Make a Hypothesis

Using the information above, make an educated guess about what type of slope will work the best. Your hypothesis should be a simple statement, such as: “A straight, diagonal slope will accelerate the marble the fastest.” (This is not necessarily the best hypothesis; it’s just an example).

Conduct an Experiment

  1. Gather a 12' length of pipe insulation (you may need to tape two 6' pieces together). Tape one end to a wall 4' above the floor.

  2. Push the track toward the wall so it resembles the first curve in the diagram below.

  3. Place a heavy object – like a brick – on the track 8' away from the wall where the track begins.

  4. Use the tape measure to measure the length of the track from the starting point on the wall to the brick. Since the track curves, it will be longer than 8'.

  5. Drop the marble from the top of the track. At the same time, start the stopwatch. Stop the stopwatch the moment you see and hear the marble hit the brick. Repeat the test a total of three times.

  6. (Optional, but recommended) Take a picture of each slope configuration before changing it for the next test. You can use these photos later when you present your findings.

  7. Pull the track a little bit away from the wall so it’s less steep, but make sure that the brick remains exactly 8' away from the wall. Remember, you’re testing which slope will accelerate the marble the fastest, so the distance between the starting point and the end point must remain the same, even the slope and total length of the track changes. Try to reduce the track length by a standard amount for each test, like 6".

  8. Test each slope configuration three times. Repeat until the track is a straight, diagonal line. The illustration below shows how the shape of the track might change.

Main resized.jpg

Setup the Controls

Controls are measures put in place to prevent unintended things from affecting your results.

Follow these procedures to ensure your data is accurate:

  1. If you mess up a test (e.g. you accidentally press the stopwatch much too late), then discard that result and test again. Record any discarded tests, and write a note about why you decided to retest.

Collect Data

Record the time of each test as accurately as possible. Match the results next to the distance the end of the track is from the wall. When finished, add up the times for each set of three tests, then divide by 3 to get an average time. For example, if the times of one slope are 2.35, 2.7, and 2.2 seconds, then 2.35+2.7+2.2 divided by 3 is an average of 2.42 (rounded to the nearest hundredth of a second).

Your data might look something like this (this is not real data; don’t use in your conclusion):

Screen Shot 2018-10-21 at 1.39.06 PM.png

Make Observations

Describe any additional observations you made during the experiment. Be sure to include things might have affected your results, such as losing the marble and replacing it midway through the experiment, or anything else unexpected.

Draw Conclusions

Look at your data and conclude which slope shape caused the marble to accelerate the fastest.

Present Findings

Present your main conclusion in a visual form, such as a series of drawings or photos that illustrate each slope shape and track length with the corresponding average travel time.

Summarize your hypothesis, experiment method, the controls you put in place, and your raw data.

Write your conclusion, and explain why you think the results are the way they are.

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