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Ch. 3 Sec. 2 “Buoyant Force” Notes 12/2/08. Buoyant Force : upward force that fluids exert on an object. causes objects to be suspend- ed in or float on top of a liquid. Buoyant Force. Archimedes’ Principal : buoyant force is equal to the weight of the fluid that the
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Ch. 3 Sec. 2 “Buoyant Force” Notes 12/2/08
Buoyant Force: • upward force that fluids • exert on an object. • causes objects to be suspend- • ed in or float on top of a • liquid. Buoyant Force
Archimedes’ Principal: • buoyant force is equal to the • weight of the fluid that the • object displaces. Man & board displace 250 N of water. What is the buoyant force on the man & board?
Object will Sink: • if its weight is greater than the weight of the water it displaces (buoyant force). Tablet displaces 2.5 N of water. The tablet weighs 5.5 N. Why does it sink? 5.5 N Buoyant force = 2.5 N
Object will float: • if its weight is less than or equal to the weight of the water it displaces (buoyant force). Buoyant force is 35N on the bottle. The bottle weighs 35N. Why does the bottle float? 35 N Buoyant force = 35 N
Density: • the mass per volume (area • taken) of an object. • Calculated using the this • equation: • density = mass / volume • d = m / v
i.e.- a 100g cylinder that takes up 20 cm3 of volume has a density of Mass = 100 g Volume = 20 cm3 d = 100g / 20 cm3 d = 5 g/cm3
Changing Density: • Changing density of an object • controls if it sinks or floats. • 1. Changing shape changes an • objects volume, changing it’s • density
2. Changing mass changes the overall density.
3. Changing volume changes the overall density.