Fast and Easy Science Fair Projects: Smaller is Stronger

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Metal washers2 paper clipsStringHardbound books (2)Fireplace MatchesPaperPencil
Metal washers
Metal washers
2 paper clips
2 paper clips
String
String
Hardbound books (2)
Hardbound books (2)
Fireplace Matches
Fireplace Matches
Paper
Paper
Pencil
Pencil

Testing tensile strength

Purpose: To discover if an object's strength has any relation to its length.

Overview: The term tensile strength means how strong something is when it is unsupported; how much tension or pressure it can take before it breaks. Steel has great tensile strength. Is tensile strength affected by length?

Hypotheses: As an unsupported span decreases in length it can support more weight.

You need:

  • large metal washers
  • 2 paper clips
  • string
  • 2 hardbound books
  • an adult
  • 2 long (fireplace) safety matches
  • paper and pencil

Procedure: Sand two hardback books upright, opening them slightly. Place them about 10 inches (25 cm) apart. Have an adult light and blow out long matches, made specially for fireplaces, so they are safe to use. Lay one match across the books. Bend open two metal paper clips so they form an "S," with a hook at the top and bottom of each clip.

     Tie a paper clip onto each end pf a short piece of string. Hang one paper clip from the middle of the match. Push the hook of the other paper clip through the hole of a large metal washer. This makes it easy to add more washers.

     Add washers until the match breaks. Write down how many the match could hold.

     Now repeat the experiment, but this time move the books closer together, about half the distance they were. The Variable is the length of the span being stressed. Will the shorter unsupported span of the match be able to hold more weight without breaking?


Results and Conclusion: Write down the results of your experiment. Come to a conclusion as to whether or not your hypothesis was correct.


Something more: Can you work out (quantify) the relationship between the length of unsupported match in inches and the number of washer needed to break it?


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