Keeping Up

Abstract

Objective

In this experiment you will test if the height of a person is related to their walking pace, and if this information can be used to estimate the height of a person.

Credits

Sara Agee, Ph.D., Science Buddies

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Introduction

A pedometer is an instrument that is often used by joggers or walkers to tell them how far a distance they have gone. The name pedometer comes from the latin words "ped" which means to walk, and "meter" which means to measure. On some pedometers when a person sets the instrument before an outing, they must enter their height into the pedometer to get an accurate reading. Why is height an important variable for measuring how far a person has walked?

One part of the answer has to do with ratios, which are fractions that are used to describe the relationship between two measurements. Our bodies have many interesting ratios in them. For example, when your arms are outstretched the distance from the tip of one hand to the other is usually equal to your height. This type of ratio is called a one-to-one (written 1:1) ratio. There are other types of ratios as well, each describing how one part of the body relates to another in size. Because the length of a person's legs is related to a person's height by a ratio, the height of a person will effect how long of a step they take. The longer each step is that you take, the more distance you will travel when walking, jogging or running. This ratio, combined with the motions involved in walking, are how pedometers measure distances.

Here is a picture of a pedometer designed just for kids to be easy to use and accurate for small steppers. (product by Silva, Sweden)

The measurements of a pedometer are based on the hypothesis that all people have common ratios and proportions, even if they are different heights. In this experiment, you can test this hypothesis by measuring the height of different individuals to see if this is related to the number of steps they take to walk a certain distance. Will the result be a ratio? Will the ratio of different volunteers be the same? Can you use the ratio to predict the height of a person by counting the number of steps they take to walk a certain distance?

Terms and Concepts

To do this type of experiment you should know what the following terms mean. Have an adult help you search the Internet, or take you to your local library to find out more!

• pedometer
• height
• distance
• estimate
• best fit
• standard

Bibliography

• Bumgardner, Wendy. 2005. "How to Set Your Pedometer." New York, NY: About, Inc., a New York Times Company. [2/15/06]
  http://walking.about.com/cs/pedometers/a/pedometerset.htm
• Bumgardner, Wendy. 2005. "How Many Steps Per Day Do Children Need?" New York, NY: About, Inc., a New York Times Company. [2/15/06]
  http://walking.about.com/od/measure/a/childsteps.htm
• Klein, Aaron. 1977. You and Your Body: A Book of Experiments to Perform on Yourself. Garden City, New York: Doubleday and Company, Inc.

Materials and Equipment

• notebook
• pencil
• sidewalk chalk
• tape measure (able to measure out 20 feet)
• graph paper
• straight edge ruler

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Experimental Procedure

1. First, make yourself a data table in a notebook to bring with you when you do your experiment. It should include a place to write each person's height and the number of steps they took when walking 20 feet in distance. You will not need to write down anybody's name, it is better to keep volunteers anonymous for a scientific study.
2. Find a place for your experiment. The ideal place would be a park with a jogging path were you can ask for volunteers as they pass by.
3. Measure out your distance for the walking test. Using your tape measure, measure out a distance of 20 feet marking the beginning and ending points with a piece of sidewalk chalk.
4. Find some volunteers for this experiment. Try to find at least ten volunteers of different heights. If you will be asking for help from people you do not know, be sure to have your parents supervision and permission to speak with strangers.
5. Measure the height of each volunteer with your measuring tape. Write down the height of the volunteer in your data table.
6. Ask each volunteer to walk from the beginning to the end while counting the number of steps they take. Write down the number of steps in your data table.
7. Politely thank each volunteer for helping you with your experiment.
8. After collecting your data, you will need to make a graph. Plot the number of steps on the bottom axis (X-axis) and the height on the left axis (Y-axis). For each volunteer, make a dot where the height and the number of steps cross. When you are done plotting your points, you should have one dot for each volunteer.
9. Do your dots almost make a line? If they do, use a ruler to draw a "line of best fit" through the dots. Do the best you can to line up a ruler through the middle of the dots and draw your line. You can use this line as a reference to estimate the height of a person based upon the number of steps they take to walk 20 feet.
10. Estimate your own height by walking from one end to the other of your 20 foot course while counting the number of steps you take. Find the number of steps on your graph and find the place on the graph where it crosses your "line of best fit." Place a bright red star on this point. Look over to the left to see which height the star matches up with, this will be an estimate of your height. Write this information in a data table:

    An Estimation of My Height Using My Experimental Data
    Number of Steps Taken (20 ft.)	Estimation of My Height (ft)	My Actual Height (ft)	Difference in Height (Est - Actual)

11. Ask your parent to measure your actual height with the tape measurer. Write this in your table. Calculate the difference between your estimated height and the actual height by subtracting one from the other. How accurate was your estimate? Is there a reliable relationship between theheight of an individual and the pace that they walk? How can this information be used?

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Variations

• Make another data table for estimating the height of a person based upon the "standard" graph that you developed. It should have a place for the number of steps, the estimated height and the actual height. Now ask for more volunteers and try to guess their height based upon your graph and the number of steps they take. How often are you correct? How accurate are your estimates?
• One factor in developing a standard in this experiment is over which distance you choose to measure the number of steps a person takes. Do you think that longer or shorter distances would give a better, more accurate standard? Do an experiment by developing separate standards, each using a different distance over which the steps are counted (10 feet, 20 feet, 30 feet, etc.). Which one gives the most accurate measurement?
• You can develop standard curves for the role of height (or some other variable) in other sporting activities. Try the height a person can jump, the distance a person can jump, the distance a person can throw a ball, etc.
• How does the speed of walking effect the number of steps required to go a certain distance? You can do an experiment where you walk the 20 foot distance slowly, moderately fast, or very fast to see if the number of steps changes with speed. Will there be more steps for slower or faster walking? What about running? How might this relate to momentum?

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• Science Fair Project Guide
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