School Login



Download Now


PhET Interactive Simulations
University of Colorado Boulder


  • Buoyancy
  • Density


When will objects float and when will they sink? Learn how buoyancy works with blocks. Arrows show the applied forces, and you can modify the properties of the blocks and the fluid.

Sample Learning Goals

  • Predict whether an object will sink or float when placed in a liquid, given densities of the object and liquid
  • Apply the definition of density to both liquids and solids
  • Relate the buoyant force on an object to the weight of liquid it displaces
  • Describe how the buoyant force is related to an object's relative density to the fluid
  • Predict the weight of a completely or partially submerged object of known mass and volume
  • Describe the forces that act on a completely or partially submerged object
  • Explain how an object that is more dense than water can be kept afloat by placing it on an object that is less dense than water
Version 1.05