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Science Launch G4 / Week 10 / Wednesday
3/6
Week 10 · Senses and Signals

Wednesday

Investigation: Catch the ruler
// How animals take in information and respond
⏱ about 15 min

Wednesday: Catch the ruler

Rocket holds a ruler above Raven's open fingers. "When I drop it, catch it as fast as you can."

He lets go. Raven snaps her fingers shut. The ruler slips a few centimeters before she grabs it.

"Ha! I caught it at 15," she says. "What do you notice that has to happen before my fingers move?"

Nova glows above the ruler. "Would you like a hint? Count the steps from your eyes to your fingers."

What you need

  • A 30 centimeter ruler
  • A partner
  • A table to rest your arm on
  • A pencil and paper
Safety first
Drop the ruler gently. Keep faces away from the drop zone.

Steps

  1. Rest your arm on the table with your hand hanging over the edge.
  2. Your partner holds the ruler so the zero end is between your thumb and finger.
  3. Watch the ruler. Your partner drops it without warning.
  4. Catch it as fast as you can. Read the number where your fingers caught it.
  5. Do three tries. Write each number.
  6. Now close your eyes. Your partner says "now" at the moment of the drop.
  7. Catch it when you hear "now." Do three tries and write the numbers.
MAKE A PREDICTION
  • Read the question.
  • Tap your answer.
If you react faster, will your catch number be smaller or bigger?
SignalTry 1 (cm)Try 2 (cm)Try 3 (cm)
Seeing the drop
Hearing "now"
FROM DROP TO CATCH
  • ?Nerves carry the message to your brain
  • ?Your fingers close on the ruler
  • ?Nerves carry a message to your hand muscles
  • ?Your eyes see the ruler fall
  • ?Your brain decides to catch
WHY THIS EXERCISEEvery catch needs a sense, nerves, the brain and muscles, all in a row.

Reading your catch data

A smaller catch number means you reacted faster.

Compare your seeing tries with your hearing tries.

Every catch needed the same chain: sense, nerves, brain, nerves, muscles.

RULER THINKING
  • Read the question.
  • Tap your answer.
Raven caught the ruler at 15 cm. Rocket caught it at 10 cm. Who reacted faster?
Why did you do three tries for each signal?
In the hearing test, your ____ took in the signal.
The ruler is caught by your hand ____.

You measured your own signal system! Tomorrow we meet animals with senses very different from ours.

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