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Observing the Coriolis Effect with a Spinning Water Drain
Watching water spiral down a drain feels mundane until your student realizes Earth’s rotation is involved. Observing the Coriolis effect with nothing more than a sink and a few drops of food coloring makes that connection concrete.
Your student spins water clockwise and then counterclockwise in a sink, adds food coloring to track the motion, and records which direction the water spirals down the drain for each trial. The results table has columns for initial spin direction, the direction water spiraled, and open notes, with two trials built in plus a written observation prompt at the bottom. This lab is well-suited for grades 5-8 and connects physical geography to fluid dynamics in a way that sticks.
The sheet fits naturally into an Earth science or physics unit study, particularly alongside lessons on weather systems, ocean currents, or hemispheric differences. Three Think More questions ask your homeschooler to explain why the spin direction changed, connect the sink behavior to winds and ocean currents, and name real-world examples where observing the Coriolis effect matters, like hurricanes. A fun fact at the bottom notes that Northern Hemisphere hurricanes spin counterclockwise while Southern Hemisphere hurricanes spin clockwise, giving your student an immediate real-world anchor for what they just recorded.
Grades 5-8 homeschoolers record drain spin direction while observing the Coriolis effect using food coloring and a sink. Instant download.
Investigating Observing the Coriolis Effect at the Sink
Usage Notes
Every material is a household item: a sink with a central drain, clear water, a stopwatch or timer, a notebook, and optional food coloring to visualize the spiral. Food coloring is the only consumable, and a small cup is listed for containing it before adding drops near the outer edge of the water. No chemicals or heat sources are involved, making this a low-supervision experiment for independent learners.
Printing Tips
Standard 20 lb printer paper works fine for pencil entries in the results table, but 24 lb copy paper keeps the sheet from wrinkling if hands are damp near the sink. Slip it into a plastic page protector and use a dry-erase marker if your student plans to run the experiment more than once before writing final answers.