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Everyday Machines / Week 03 / Thursday
4/6
Week 03 · Lock and Key

Thursday

Test it: which key opens it?
// A key's shape lifts the pins just right
⏱ about 15 min

Thursday: Test It, Which Key Opens It?

Rocket lines up three keys in a row.

"One of these is the real one," Rocket says.

Raven tries each key, slowly and gently.

"What do you notice? Only one turns," Raven says.

Nova blinks. "Would you like a hint? Look at the bumps on the winner."

A fair test

A fair test changes only one thing.

Today we change the key. The lock stays the same.

Same lock, same gentle turn, same person.

You need

  • The approved padlock and its key
  • Two other keys that fit in the slot
  • A pencil for the table
Safety first
A grown-up turns each key gently. Never force a key.
Never lock anything onto a person or a pet.
Keys and small locks stay away from younger siblings.
  1. Mix up the three keys.
  2. Pick one key. A grown-up slides it in.
  3. The grown-up turns gently. Did the lock open?
  4. Write yes or no in the table.
  5. Try the next key. Then the last one.
  6. Do the whole test one more time.
KeyTry 1: did it open?Try 2: did it open?
Key A
Key B
Key C
For a grown-up
Turn each key with the same gentle twist.
Stop at once if a key sticks.
WHAT HAPPENED?
  • Read the question.
  • Tap your answer.
How many keys opened the padlock?
What did we change in this test?
Why did the wrong keys fail?
Why did we test two times?
SentenceTrue or false?
A fair test changes only one thing.?
We used a different padlock for each key.?
Only the right key opened the padlock.?
A grown-up turns the keys.?
WHY THIS EXERCISEA fair test makes the result trustworthy.
Draw the three keys. Circle the one that worked.
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 lock in your own words.

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