Science

The Physics of a Spill-Proof Cup

The Mighty Mug isn't completely unspillable, but it gets pretty damn close. Here’s how.

The tumbler's primary weapon is a suction cup, which uses atmospheric pressure to form a rubber seal with the surface of the table.

  • 01
    The atmosphere is like a bunch of tiny balls that are constantly moving around—and when they collide with a surface, they exert (also tiny) force in the direction they were traveling.
  • 02
    There's less air pressure underneath the suction cup than above it, which creates a net downward force.
  • 03
    That pressure differential creates a healthy grip on the table, but the big question is: what does it take to knock the cup over?
  • 04
    When we push the cup near the top like this, we see all the forces at play.
  • 05
    If we assume the suction force and contact area, we can calculate the suction force.
  • 06
    It takes 11 pounds of force to knock the mug over—or roughly five times the force of a normal tap. In other words, you *can* do it, but you're not gonna do it accidentally. Feel free to gesticulate wildly\!

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