Why Do Drinks Always Run Down the Side of the Cup?
Science ABC
Sep 23, 2026 10:58
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Chapters
Why does your tea dribble down the side of the cup instead of pouring cleanly into the glass? In this video, we explain the "teapot effect" in simple words — the tug-of-war between adhesion and cohesion, why slow pours cling to the container, how pouring speed and angle decide where the liquid goes, and why a sharp-edged spout gives a clean pour.
Whether you're a student learning about surface tension, a curious mind who's tired of wiping up spills, or just someone who loves everyday physics, this explainer shows the hidden science behind a very ordinary mess.
CHAPTERS:
WATCH NEXT:
▶ How Buoyancy Works – https://youtu.be/MbPrXOp2qq0
▶ Archimedes Principle – https://youtu.be/wChr0hCga5g
▶ Magnus Effect – https://youtu.be/AHeu-3lGzQQ
KEY TOPICS COVERED:
• The teapot effect: why liquids run down the side of a container
• Adhesion vs cohesion explained with water
• Intermolecular forces and surface tension
• How adhesion forms a meniscus in a test tube
• Why gravity must overcome adhesive forces for a clean pour
• How pouring speed and angle change the flow
• Why sharp-edged spouts pour cleaner than smooth rims
#TeapotEffect #SurfaceTension #Physics #FluidDynamics #EverydayScience #ScienceABC
REFERENCES:
https://openstax.org/books/college-physics-2e/pages/11-8-cohesion-and-adhesion-in-liquids-surface-tension-and-capillary-action
https://www.usgs.gov/water-science-school/science/adhesion-and-cohesion-water
https://en.wikipedia.org/wiki/Teapot_effect
Voice Over: John Staughton (https://www.fiverr.com/jswildwood)
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Science & Technology
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