Saturday, October 5, 2013

Making Mythbusters: Time for a Toast

As part of our homeschool Cooperative for Science and Math, we've been exploring the experiments featured on the Mythbusters show. Last week, we decided to test one of my absolute favorite myths: "Toast will always fall buttered side down."

There are few ways to look at this. The first is as a coin toss. Flip a coin and you should have about the same odds for a tails up as for a heads. This is basic probability. You can test it yourself. Actually I highly recommend that you do! (Mythbusters: The Explosive Exhibition has a lesson plan, called "Flip It," all about it.)

Get some friends together, as we did in class, and collect as much data as you can. Aim for 100 coin tosses, making a simple tally sheet to record which flips come out heads or tails. Then you can compare the ratio of heads to tails, create a bar graph, even determine the percentage error!

Now that you know what the data looks like if both sides of the coin -- or toast, in this case -- are equal, what happens if you make the sides unequal.

There are a lot of questions you could ask, as you design your experiment. You want to make sure you know your variables and control for as much as possible. Some questions we had:

  • Do the pieces of toast need to be the same shape? Can we control for the the shape of the toast? How?
  • Does the mass of each piece of toast matter? How can we control for the mass?
  • Does the amount of toasting affect how the toast falls? Do they need to be equally browned on both sides?
  • Does the amount of butter on each piece need to be the same? How can we control the amount of butter on each piece? Does it matter how we apply the butter? Can we use something other than butter -- such as vegetable shortening, peanut butter or jelly? 
  • Does the height from which the toast is dropped make a difference? Does it matter how the toast is held when it is dropped? Does it matter if the same person does the drop each time?
  • What would happen if we spread butter on both sides of the bread? Or none?
  • How many pieces of toast should we drop before we can feel sure about our results? 
The toast myth gives a lot of room for experimental design. Make sure you let the kids take the time to decide what questions are most important to them.

We decided to use 1 tsp. of vegetable shortening (easy to measure) on one side of toast, dropped from the height of a step ladder by an adult, with the toast held vertically before the drop. We further tested the affect of the shape of the toast on the fall -- half of the toast was selected for similarity by sight; the other half was cut to a uniform circle using a cutter. We dropped 8 pieces of toast for each shape. 

In the end, our results were very much the same as the Mythbusters results from the show! We didn't get exactly even results. In fact we found toast was more likely to fall with the buttered side up. There are some really interesting reasons for this: period of rotation, moment of inertia and angular momentum all play a role. 

Given enough time to explore, how many variables can you control? Well, we only had an hour, but this could easily be a whole day project. (And time well spent.)

So next time you're having breakfast, maybe you can have some science with your coffee and tea. Enjoy!

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