2B20.65 Bag Blowup


Small forces on small areas transfer to large forces on large areas


When a bag is inflated, it lifts a weight placed on top of it.



  • [1] Weight
  • [1] Sealed plastic bag with a tube attached
  • [1] Plank of plywood that is roughly the same size as the bag

Important Notes

  • A textbook works very well as a weight


  1. Place the bag on the table.
  2. Place the piece of plywood on the bag to protect it from the weight.
  3. Place the weight on the plywood.
  4. Blow into the tube to inflate the bag. The weight will be lifted by the inflating bag.

Additional Resources


  • PIRA 2B20.65


  • Don't attempt this at home!

Last revised

  • 2020


  • Original construction: a tube was inserted into one corner of a sturdy square storage bag and the bag was sealed with tape. The bag is roughly the size of a first year physics text book.

Related AV

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If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.