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• Science Fair Project Guide

Project Summary

Difficulty	3
Time required	Very Short (a day or less)
Prerequisites	None
Material Availability	Readily available
Cost	Very Low (under $20)
Safety	No issues

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Sponsor

Sponsored by a generous grant from Seagate

Objective

In this experiment you will use an inclined plane to test the walking speed of two differently sized Slinkies.

Introduction

The Slinky is a classic American toy, with roots in Pennsylvania. The inventor of the Slinky was a retired Navy engineer named Richard James. He initially thought the bouncy springs would be useful for supporting sensitive instruments onboard rocking ships at sea. But when the Navy had no interest in his springs, his wife Betty had a better idea. She thought up a catchy name and Slinky the toy was born in 1945.

The classic Slinky— fun for all ages!

The Slinky has a unique ability to "walk" down steps or a sloping surface. This type of sloping surface is also a simple machine called an inclined plane. How will these two mechanical systems interact? In this experiment you will make a simple inclined plane to test the walking speed of two differently sized Slinkies, the original Slinky and the Slinky Jr.

Terms, Concepts and Questions to Start Background Research

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!

• inclined plane
• coil
• diameter
• angle
• critical angle
• protractor

• How do I build an inclined plane?
• What angle is best for the Slinky to slink down the inclined plane?
• Will Slinkies of different diameters use the same angle?

Bibliography

Read about how the Slinky was invented from this site for young inventors at MIT:

• MIT, Date Unknown. "Inventor of the Week: Slinky," Lemelson-MIT Program: Massachusetts Institute of Technology, School of Engineering. [accessed February 10, 2007] http://web.mit.edu/Invent/iow/slinky.html

Check out the Slinky Science Teaching Guide, developed by engineers at Conoco Phillips:

• TeachingTools.com, 2003. "Racing Slinky's," Slinky Science Teaching Guide, Conoco Phillips [accessed February 2, 2009] http://www.teachingtools.com/NR/rdonlyres/E25B779A-E642-4393-8148-A8B0D8183552/0/Slinky_Science.pdf

This project was based on a project by Erica Byrne and maintained by Bob Barrett:

• Byrne, E., Date Unknown. "Slinky Walking Speed vs. Angle," Slinky Home Page [accessed February 10, 2007] http://153.42.40.32/~barrett/speed.htm

Materials and Equipment

• large, dense cardboard sheet or a piece of plywood
• stack of books
• metal Slinky
• metal Slinky Jr.
• protractor
• stopwatch

Experimental Procedure

1. For this experiment you will need to write your results in a data table. You will need to write down the type of Slinky used, the angle of the plane, the number of flips, the time in seconds and the Flips per Minute:

   Slinky
   Angle	Number of Flips	Time (seconds)	Flips per Minute
   30o

   Slinky Jr.
   Angle	Number of Flips	Time (seconds)	Flips per Minute
   30o

2. To make your adjustable inclined plane, rest one end of your plane (either a stiff sheet of cardboard or a piece of plywood) on a stack of books. To adjust your angle, simply add or remove books to the stack. Adding books will increase the angle and removing books will decrease the angle.
3. Measure the angle formed where the base of the plane meets the floor with a protractor. Begin by setting the angle to 30 degrees.

4. Get your stopwatch ready and set the Slinky at the top of the plane.
5. Release the Slinky and start the stop watch. Count the number of flips and stop the watch when the Slinky completes its last flip before the end of the plane. Write down the number of flips and the time in seconds in your data table.
6. You will calculate the speed of the Slinky in Flips per Minute. To do this calculation, divide the number of seconds in a minute (60) by the number of seconds you measured. Then multiply your answer by the number of flips you counted. For example, if I counted 3 flips of my Slinky in 10 seconds,
   then 60 / 10  = 6 and 6 x 3 = 18 Flips per Minute. Write this calculation in your data table.
7. Test the Slinky Jr. at the same angle, make your measurements and calculations, and record your data.
8. Change the angle of the inclined plane and repeat the experiment with each Slinky.
9. Make a graph of your results by putting a scale of the angle on the bottom (x-axis) of the graph and a scale of the walking speed in Flips per Minute on the left side (y-axis) of the graph. Make a dot for each data point on your graph. Make the Slinky dots in one color and the Slinky Jr. dots in a contrasting color. Then connect the dots for each respective color.
10. How do your results compare? Is the bigger Slinky faster or slower? Were the movements the same or different? How did the walking speed change as the angle increased or decreased?

Variations

• In this experiment you compared the movements of two differently sized Slinkies, but you can also compare Slinkies made of different materials. Try the experiment again with the plastic Slinky and Slinky Jr. Are your results the same or different?
• There are many ways to use a Slinky for a science experiment:
  • Put the two ends on the floor and jump to find out how you can use the Slinky as a wave detector.
  • You can use the Slinky to study compression waves by wiggling it back and forth.
  • If you bang on the Slinky you can generate sound. Can you make different pitches?
  • Slinkies have also been used as giant antennae.
  • What else can you think of?
• Advanced students can use linear regression to further analyze the data. Can you define an equation that expresses the relationship between the angle of incidence and the walking speed for this system? What is the error in your experiment? Are your results significant?

• For more science project ideas in this area of science, see Mechanical Engineering Project Ideas.

Credits

Sara Agee, Ph.D., Science Buddies

Sources

This project was based on a project by Erica Byrne and maintained by Bob Barrett:
Byrne, E., Date Unknown. "Slinky Walking Speed vs. Angle," Slinky Home Page [accessed February 10, 2007] http://153.42.40.32/~barrett/speed.htm

Last edit date: 2009-02-02 09:30:00

Career Focus

If you like this project, you might want to think about career opportunities in Mechanical Engineering.

Mechanical engineers are part of your everyday life, designing the spoon you used to eat your breakfast, your breakfast's packaging, the flip-top cap on your toothpaste tube, the zipper on your jacket, the car, bike, or bus you took to school, the chair you sat in, the door handle you grasped and the hinges it opened on, and the ballpoint pen you used to take your test. Virtually every object that you see around you has passed through the hands of a mechanical engineer. Consequently, their skills are in demand to design millions of different products in almost every type of industry. Learn more about this career: Mechanical Engineer.