BUOYANT FORCE

What is buoyant force: The upward force that fluids exert on all matter This includes air

Buoyant force is caused by differences in fluid pressure Archimedes' Principle – buoyant force of an object in a fluid is an upward force equal to the weight of the volume of fluid that the object displaces Displace means “to take the place of”

Weight vs. Buoyant Force An object in a fluid will sink if it has a weight greater than the weight of the fluid that is displaced. Sinking happens when weight is greater than the buoyant force acting on it Floating happens only when it displaces a volume of liquid that has weight equal to the object's weight Buoyant force opposes gravity

An object will float or sink... Based on its density (mass/volume) Things that sink in water are more dense than water Things that float in water are less dense In air, most substances are more dense than air Exception is helium (balloons)

The Mystery of Floating Steel Steel is almost eight times more dense than water, yet huge steel ships cruise the oceans. The shape of the ship, bowl shape, increases volume of the ship which decreases the ships density Ships overall density if less than the density of water, allowing it to float

Submarines A special kind of ship that can travel on the surface of the water AND underwater Special tanks that open to allow water in, adding mass, causing it to sink. Crew members can control the amount of water taken in, changing the density and depth in its ocean Compressed air is used to low water out

How is a fish like a submarine? Like a submarine, some fish adjust their overall density in order to stay at a certain depth in the water using their swim bladder The swim bladder is filled with gases produced in the fish's blood, it inflates to decrease density Sharks do not have a swim bladder so they have to constantly swim to keep from sinking