October 1995: Painless Science Fair Projects

Instructions for Students

1. Sit on the chair with your forearm on the tabletop and your writing hand extending over the edge of the tabletop.
2. Ask your helper to hold the ruler so that the bottom of the stick (the zero end) is just above your hand.
3. Place your thumb and index finger on either side of, but not touching, the bottom of the ruler.
4. Ask your helper to drop the ruler through your fingers without telling you when it is going to be dropped.
5. After the ruler is released, try to catch it as quickly as possible between your thumb and fingers.
6. Observe the number on the ruler just above your thumb. Record this number as the reaction distance.

Results

The distance the ruler falls varies with each individual. Why? You might start by asking students what factors they think affect this distance. You might explain how the mind and body work together to catch an object. Your explanation might go something like this.

When the ruler begins to fall, a message is sent to the brain. Like a computer, the brain takes this input information and, in fractions of a second, sends a message telling the muscles in the hand to contract. The distance the ruler falls can be different for each individual because it depends on the time it takes for these impulses to be sorted out by the brain, the time it takes for the output message to be received by the hand's muscles, and the time it takes for the muscles to react.

Figure 2 Data chart (Top) and
reaction time graph (Bottom)

The sensory nerves in the eye start this relay with messages called nerve impulses. The first stop is in the largest section of the brain called the cerebrum. The cerebrum is where all thoughts occur and where input from sensory nerves is interpreted. The cerebrum sends a message (nerve impulse) to another section of the brain called the cerebellum, which brings together all the muscle actions necessary to grasp the ruler. This does not have anything to do with how smart you are; instead, it depends on differences in hand-eye coordination.

Changing an Experiment Into A Project

The "cookbook" experiment is a foundation, but it is only a foundation - not a science project. It can be developed into a project by using the exploring question - "I wonder what would happen if. . . ?"

Start this type of thinking by asking students the question "I wonder if using a different hand would change your reaction time?" Have each group change hands and repeat the experiment. Discuss the results. (Be sure to encourage students to always get adult approval before trying their own exploring questions.)

You now have enough information to express the problem for the project, which could be, "What influences the time it takes you to catch a falling object?" Now is also the time to introduce the term hypothesis. A hypothesis is simply a statement expressing your best scientific guess, or series of guesses, that answer the problem question. It can even be a list of "maybes."

One way to proceed could be to ask the class to guess the different factors that might affect falling time. List these on the chalkboard, then discuss which ones will be used for your project. Explain the concept of variables and discuss why no project can examine all the variables. Therefore, it's up to the students to determine which factors they want to study. Safety, time, and the supplies available may be reasons to delete some suggestions.

For this project a hypothesis could be: The things that influence the time it takes to catch a falling object are practice, distractions, age, drugs, and which hand is used.

Each item on the hypothesis list can be expressed as an exploring question, like "I wonder if practice would change the reaction time?" Have one or two students in each group repeat the experiment ten times. Introduce a data chart to record the reaction time for each trial and a reaction time graph (Fig. 2) as two ways to display the results.

The next exploring question might be "I wonder if distractions affect the results?" This hypothesis could be studied by having one member of the group ask questions to the student being tested during the experiment. The questions could be simple math problems, or anything else that requires enough thought to be distracting. Compare the student's reaction time with and without distractions.

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