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Experiment

Waterfall Cup

A plastic cup with holes in the bottom, and pouring water through it becomes an hour-long investigation.

Ages 1–515–40 min1–2 kidsHousehold items

Poke 1, 3, or 5 small holes in the bottom of a plastic cup. Child fills the cup and watches water stream through. Make several cups with different hole patterns. Compare: more holes = more streams but less pressure per hole. Occupies very young children for extended periods.

What you need

  • plastic cups
  • skewer or nail for holes (parent prepares in advance)

How to do it

  1. 1Ready to make a waterfall with these cups?
  2. 2Give the cups to the child. Fill from the bath. Watch the streams.
  3. 3Compare the cup with one hole against the cup with five. Which streams go further?
  4. 4Try different heights. Does higher make the streams stronger? Let them find out.

Variations

  • Korb-Tür: If they won't pour — just hold the cup and watch you pour. They can direct where it goes. Pouring is optional.
  • Ausstieg: Stack the cups. 'Fill the top one and watch it travel all the way down.' One final chain, then done.

💡 Parent tip

Prepare the cups before bath time. Holes should be small (2mm) so the cup doesn't drain immediately. This turns a 30-second craft into a 30-minute activity.

What your child develops

  • Fluid dynamicswater pressure, hole size, and height all affect stream behaviour
  • Cause and effectchanging one variable changes the outcome
  • Sustained attentionimmediate feedback of water behaviour keeps young children engaged

Safety notes

  • Adult makes the holes. Never leave young children unattended in the bath.

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