Buoyancy

• Buoyancy


  How well something floats or sinks
• Positively buoyant


  Something that is able to float
• Negatively buoyant


  Something that sinks
• Generally, if something is light it floats or is positively buoyant, if it's heavy then it sinks or is negatively buoyant
• Density


  The amount of stuff or mass something has inside of it compared to its volume or size
• Density examples


  • Bucket full of sand is more dense than an empty bucket
  • Bowling ball has more mass than a basketball
• Archimedes' principle


  When an object is placed in water, it experiences an upward buoyant force equal to the weight of the water displaced by the object
• Archimedes discovered this principle when he noticed the water level rising as he sat in the bath
• If an object is heavier than the amount of water it displaces


  The object will sink
• If an object is lighter than the amount of water it displaces


  The object will float
• Cruise ships float because they are very large and most of the ship is hollow, so it's not as dense as you might think
• Submarines drive by allowing water to fill part of the submarines called ballasts, and the air gets vented out until the density of the sub is enough to make it sink
• Ships also use ballasts for balance, without them they have a tendency to tip in windy weather