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Everyday Machines / Week 02 / Thursday
4/6
Week 02 · The Zipper

Thursday

Test it: slider or fingers?
// Rows of hooks and a slider that is a wedge
⏱ about 15 min

Thursday: Test It, Slider or Fingers?

Rocket sets a timer. "Fingers first!" he says.

He tries to press the teeth together one by one.

Then Raven zips the same zipper with the slider.

"What do you notice? Which way was faster?" Raven asks.

Nova blinks. "Would you like a hint? Count how many teeth locked."

A fair test

A fair test changes only one thing.

Today we change the tool: fingers or slider.

Same zipper, same person, same count of ten.

You need

  • The approved zipper from yesterday
  • A grown-up to count to ten
  • A pencil for the table
Safety first
Press gently. Teeth can pinch skin.
Do not force the slider if it sticks.
A grown-up fixes a stuck zipper.
  1. Open the zipper all the way.
  2. A grown-up counts slowly to ten.
  3. Try to lock teeth with your fingers only.
  4. Count how many teeth locked. Write it down.
  5. Open the zipper again. Now use the slider for ten counts.
  6. Count the locked teeth. Write it down.
ToolTry 1: teeth lockedTry 2: teeth locked
Fingers
Slider
For a grown-up
Keep the count the same speed each time.
If fingers lock zero teeth, that is a real result!
WHAT HAPPENED?
  • Read the question.
  • Tap your answer.
Which tool locked more teeth in ten counts?
What did we change in this test?
Why did the slider win?
Why did we try two times?
SentenceTrue or false?
A fair test changes only one thing.?
We used a different zipper for each tool.?
The slider locks teeth faster than fingers.?
A grown-up fixes a stuck zipper.?
WHY THIS EXERCISEA fair test makes the result trustworthy.
Draw your two tries: fingers and slider.
OUR FAIR TEST
  • Tap a card.
  • Then tap its spot.
1First
2Next
3Then
4Last

You tested a machine fairly. That is real science!

Tomorrow you explain the zipper in your own words.

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