Cup Water Clock

What you need

• Clear cups, 3 paper or plastic cups
• Water, about 2 cups (500 ml)
• Phone, 1 timer
• Crayons or markers, 1 marker
• Towel, 1
• Plate or tray, 1 tray
• Jug, 1
• Glass, 1 clear glass
• Pencil, 1, for poking the hole
• Pin, 1, for a grown-up

How to do it

Grown-up prep: Set up near a sink or outside, with a towel on the floor so spilled water is not slippery. Have a pin ready for a smaller hole, since pencil tips and pins are sharp.

1. Poke a small hole in the bottom of a cup with a pencil.
2. Hold the cup over the glass and pour in water. Start the timer!
   Ask: How long do you think the water will take to empty?
3. Too fast? A grown-up makes a smaller hole in a fresh cup with a pin. A grown-up does this
4. Too slow? Widen the hole a little, or pour in less water.
5. Test and adjust until your cup empties in exactly one minute.
6. Fill the cup and start the timer. Mark the water level every ten seconds.
   Ask: Will the ten second lines be evenly spaced? Why or why not?
7. Test your marked clock against the timer three times.
8. Now show your family your clock, or try making a two minute one!
   Ask: What did you notice about how the lines were spaced, and why do you think that happened?

Play it again

• Two minute clock: use a bigger cup and a smaller hole to time two minutes.
• Hole race: make cups with different hole sizes and predict which empties first.
• Timer challenge: use your clock to time a task, like tying a shoe, and beat your best.