Buoyancy
Fluid Pressure and Hydraulics
Compression of a gas
Why a gas can compress:
• The gas must be enclosed in a sealed container with strong walls so the molecules can distribute themselves through the container.
• There is so much space between gas particles, so even after they are compressed, space between the particles still exists so they still act like a gas.
• An external force is applied to the gas to push the particles together.
Why other states of matter can’t be compressed
• The particles are almost as close as possible so when a force is applied to them, they can’t move much closer together.
• Gas can be compressed because there is lots of space between particles.
Advantages of Compression
Gas can exert a counter force back when compressed. This is useful for:
• Car tires – The tires push back against the weight of a car otherwise they would just collapse.
• Air bags – They absorb the shock of a crash to protect passengers.
• Shock absorbers in a vehicle – They absorb the force from hitting bumps in the road.
How buoyancy and density are related:
The buoyant force of a liquid and a gas depends on density. A liquid or gas that is more dense, can support more weight per volume than a liquid or gas that is less dense.
Example : Salt water is more dense than fresh water. Salt water can support more weight per volume than fresh water…so you would float better in salt water than fresh.