how do boats float – Evolution Zone

Question: how do boats float

Asked by jackc51xbox to Betul, Bridget, Ceri-Wyn, Maria on 24 Jun 2010 in Categories: General.
- Bridget Waller answered on 24 Jun 2010:
  
  Hmm. Something to do with the displacement of the water where the boat is positioned… I remember this from GCSE physics but am struggling to put it into words. Fellow scientists, help?
- Ceri-Wyn Thomas answered on 24 Jun 2010:
  
  Some things float because they are less dense than water. Wood is an example of such a substance that is less dense than water, so it floats, and therefore boats made of wood will float.
  
  But boats are also made of steel and iron, which is more dense than water, so how do these float? When you put something in water, it pushes the water aside. The water pushes back to try and regain its original shape (i.e. a flat surface). It all depends on the amount of water displaced – the force the water exerts to push the boat up is equal to the mass of water displaced, so as long as this is greater than the weight of the boat, it will float. When designing boats, engineers will make sure that this is always the case (by a considerable margin), so the boat will float. Of course, if a metal boat gets filled with water, it
  won’t be displacing nearly as much water, so the force keeping it up will reduce, and the boat will sink.

Question: how do boats float