• Question: where doe up-thrust come from?

    Asked by to Claire, Elizabeth, Manolis, Mark, Zach on 14 Mar 2014. This question was also asked by .
    • Photo: Zach Dixon

      Zach Dixon answered on 14 Mar 2014:

      The definition of upthrust is
      ‘The upward force that a liquid or gas exerts on a body floating in it.’

      This page explains it quite nicely
      http://www.schoolphysics.co.uk/age11-14/Matter/text/Archimedes_/index.html

      In short, it is the force pushing up on an object. Gravity is the force pulling down on the object. If the forces of gravity and upthrust are the same on an object it will stay where it is. If gravity is greater it will go down, if upthrust is greater it will go up.

      I hope that helps!

    • Photo: Mark Wallace

      Mark Wallace answered on 14 Mar 2014:

      When a force acts on an object, another force acts in the opposite direction. So if you blow up a balloon and then let it go, the air rushes out. As the air rushes out in one direction, there’s a force in the opposite direction that propels the balloon across the room.

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