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Science Launch G4 / Week 06 / Wednesday
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Week 06 · Wave Patterns

Wednesday

Investigation: Rope and pan waves
// Amplitude, wavelength and waves that move things
⏱ about 15 min

Wednesday: Rope and pan waves

Rocket ties one end of a jump rope to a chair leg. He grabs the other end and shakes it wildly.

The rope flops and tangles. "Hmm," he says. "That is not a pattern."

Raven takes the rope and moves her hand up and down, steady as a clock. Smooth waves roll down the rope.

"What do you notice about a steady hand?" she asks.

Nova hums. "Would you like a hint? Change one thing. First change how big you shake. Then change how fast."

What you need

  • A jump rope or a long piece of string
  • A heavy chair
  • A baking pan with about two finger widths of water
  • A bottle cap or a small toy that floats
  • A pencil
Safety first
Shake the rope along the floor, away from people and lamps.
Wipe up spilled water right away so nobody slips.
Nothing goes in your mouth.

Steps

  1. Tie one end of the rope to the chair leg. Pull the rope almost straight along the floor.
  2. Move your hand up and down a small amount, at a steady speed. Watch the wave height.
  3. Now move your hand up and down a big amount. Watch the wave height again.
  4. Next, move your hand slowly. Then move it quickly. Watch the space between crests.
  5. Float the bottle cap in the middle of the pan of water.
  6. Tap the water at one end of the pan with the pencil. Watch the cap.
MAKE A PREDICTION
  • Read the question.
  • Tap your answer.
You move your hand up and down a bigger amount. What will change?
When the ripples reach the floating cap, what will it do?
What I didWhat I noticed
Small shake
Big shake
Slow shake
Fast shake
Tapped the pan
When you shook the rope faster, did the crests get closer together or farther apart?
WHY THIS EXERCISEShaking faster squeezes more crests onto the rope, so the wavelength gets shorter.

What your waves showed

A bigger up and down motion made taller waves. That is a bigger amplitude.

Shaking faster put crests closer together. That is a shorter wavelength.

The floating cap bobbed when the ripples reached it. Waves can make objects move.

ROPE WAVE RESULTS
  • Read the question.
  • Tap your answer.
You shook the rope slowly. What happened to the wavelength?
Why did you change only one thing at a time?
StatementTrue or false?
A small shake made small waves.?
A fast shake made a longer wavelength.?
Tapping the pan made ripples move toward the cap.?
WHY THIS EXERCISEBigger shakes give bigger amplitude, and faster shakes give shorter wavelength.

You made wave patterns with your own hands. Tomorrow we compare waves using numbers.

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