Topic 6 Flashcards
Buoyancy and Buoyant Force
Buoyancy- the tendency to rise or float on a fluid(N)
Buoyant Force- The upward force exerted on objects submerged in or floating on a fluid(N)
Gravity vs Buoyancy
Gravity is a force that pulls down and buoyancy is a force that pushes up
Anti- Gravity
Floating
When an object does not fall in air or sink in water, but remains suspended in a fluid
Sinkers and Floaters
Water can support things with higher density is the mass is spread over a large enough area
Average Density
The total mass divided by the total volume
(eg) ships have massive hulls, but they float because they are hollow
Factors affecting buoyancy
- Density of the fluid
- Surface Area
- Design of object
Buoyant force in Air
The buoyant force in air is much smaller than in liquids. Although they are very far apart, they are still close enough to support some objects.(eg, the good year blimp, hot air balloon.
Benefits of Average density
Enables objects that would otherwise sink, float
Also helps floating objects to sink.
For examlpe a swim bladder or a submarine.
Archimedes Principle
The buoyant force acting on a submerged object equals the weight( force of gravity) of the fluid displaced by the object.
Does not depend on the weight of the object, but the weight of the displaced fluid( solid iron cube and hollow iron cube with same volume = same buoyant force)
Neutral Buoyancy
When the buoyant force = the gravitational force
Buoyancy and Density
The more dence a liquid the more buoyant force it has
The particles are closer together , more tightly packed
Hydrometer
Device to measure liquid density
Will extend further out of a liquid if it has a higher density and will sink lower in if it has a lower density
Formula for buoyancy
Buoyant force= weight in air - weight in liquid
1 - 0.5 = 0.5N of force
