Floating and Buoyancy

1
Floating and Buoyancy

• Objectives
• To learn
• the effects of buoyancy on a diver
• the factors that control buoyancy
• the techniques for controlling buoyancy

2
Laws of buoyancy

• Were formulated by the Greek philosopher,
  Archimedes.
• Archimedes Principle statesthe amount of
  buoyancy of an object depends on the weight of
  the fluid that it displaces.
• Displace a greater weight of water-float
• Displace a lesser weight of water-sink

3
Floating and Buoyancy-Types of buoyancy

• Positive buoyancy- things tend to float
• Negative buoyancy-things tend to sink
• Neutral buoyancy- things neither float nor sink,
  but hang in the water column

4
Factors that Influence Buoyancy

• Volume of the object
• Density of the object
• Density of the fluid in which the object is
  placed.
• Salt water _at_ 64/cu.ft. is more dense than fresh
  water _at_ 62.4/cu. Ft.
• Salt water because of its density has more
  buoyant force than fresh

5
Factors that Influence Buoyancy

• When a diver that is weighted to be neutrally
  buoyant in salt water dives in fresh water, he
  will have to remove weight in order to be
  neutrally buoyant.
• Wetsuits and BCs add volume without adding much
  weight, therefore increase buoyancy

6
Buoyancy Control

• Lungs give humans about 10 pounds of buoyant
  force.
• Much buoyancy control can occur by changing the
  volume of air in the lungs.
• Inhale to increase buoyancy
• Exhale to decrease buoyancy

7
Changes in Buoyancy

• When wearing a wetsuit, a diver will become less
  buoyant the deeper the dive
• The wetsuit is compressed, reducing the volume,
  thereby reducing the buoyancy.
• As the diver ascends, the compression is relieved
  and the suit becomes more buoyant
• Care must be taken on ascent, especially in
  venting air from the BC.