The Water Clock | Science Fenns

Start the drip

Water runs from the top jar to the bottom jar. Pick a hole. Press start. A mark appears on the bottom jar every minute.

A-

B-

C-

✓Start the water clock.
✓Make four minute marks and look at the spacing.
✓Try the small hole, the middle hole and the big hole.

Grandpa checks the drip and grins. A clock that runs on gravity and patience. Good work.

Why it works

A water clock tells time by how much water has dripped. The drip is the clock. The jar is the dial.

A small hole lets water out slowly. A big hole lets it out fast. So a small hole makes a clock that lasts longer.

Now watch the marks. They do not sit evenly. When the top jar is full, the water pushes hard and drips fast. As it empties, the push gets weaker and the drip slows down.

Grandpa. The old clockmakers learned this the hard way. They made the jar narrow at the bottom so the clock kept better time.

Toby counts the minutes

Grandpa's notebook

A water clock tells time by dripping.

A smaller hole means a slower clock.

The drip is fast when the jar is full and slow when it is almost empty.

Big word for the day. Pressure. The push of the water above the hole.