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Float Density igcse float sinking buoyancy
- 1. Floating and Sinking Floatingand Sinking
- 2. The Titanic The Titanic Whatdo you know about the Titanic? What do you know about the Titanic? How is it possible that a huge ship can How is it possible that a huge ship can easily float in water under certain easily float in water under certain conditions and then in a few hours conditions and then in a few hours become a sudden wreck? become a sudden wreck? Buoyancy!! Buoyancy!!
- 3. Buoyancy Buoyancy Water exerts aforce called a buoyant Water exerts a force called a buoyant force that acts on a submerged object. force that acts on a submerged object. The buoyant force acts in the upward The buoyant force acts in the upward direction, against the force of gravity, so direction, against the force of gravity, so it makes an object feel lighter. it makes an object feel lighter.
- 4. Buoyancy Buoyancy As you cansee in the picture, a As you can see in the picture, a fluid exerts pressure on all fluid exerts pressure on all surfaces of a submerged surfaces of a submerged object. Since the pressure in a object. Since the pressure in a fluid increases with depth, the fluid increases with depth, the upward pressure on the upward pressure on the bottom of the object is greater bottom of the object is greater than the downward pressure than the downward pressure on the top. The result is a net on the top. The result is a net force in the upward direction. force in the upward direction. This is the buoyant force. This is the buoyant force.
- 5. Submerged Objects Submerged Objects Submergedobjects take the Submerged objects take the place of a volume of fluid place of a volume of fluid equal to it’s own volume. equal to it’s own volume. Objects that float on top of Objects that float on top of the water only take the the water only take the place of the volume of place of the volume of fluid equal to the volume fluid equal to the volume of the amount of the of the amount of the object in the fluid. object in the fluid.
- 6. Archimedes’s Principle Archimedes’s Principle Archimedes’sPrinciple relates the amount of fluid a submerged object displaces to the buoyant force on the object. Archimedes’s Principle states that the buoyant force on an object is equal to the weight of the fluid displaced by the object.
- 7. Floating and Sinking Floatingand Sinking There is always a downward There is always a downward force in a submerged object, force in a submerged object, the object’s weight. the object’s weight. If the weight of the object is If the weight of the object is greater than the buoyant greater than the buoyant force, the net force on a force, the net force on a submerged object will be submerged object will be downward and the object downward and the object will sink. will sink.
- 8. Sinking and Floating Sinkingand Floating The object will only The object will only sink deep enough sink deep enough to displace a to displace a volume of fluid with volume of fluid with a weight equal to its a weight equal to its own. At that point, own. At that point, it will stop sinking it will stop sinking deeper and will deeper and will float. float.
- 9. Floating and Sinking Floatingand Sinking If the weight of the If the weight of the object is less than the object is less than the buoyant force, the buoyant force, the object will float. object will float. If the weight of the If the weight of the object is exactly equal object is exactly equal to the buoyant force, to the buoyant force, the two forces are the two forces are balanced. balanced.
- 10. Density Density The density ofa substance is its mass per The density of a substance is its mass per unit volume. unit volume. Density = Density = Mass Mass Volume Volume An object that is more dense than the fluid An object that is more dense than the fluid in which it is immersed sinks. An object in which it is immersed sinks. An object that is less dense than the fluid in which that is less dense than the fluid in which it is immersed floats to the surface. it is immersed floats to the surface.
- 11. Density Density If the densityof an object is equal to the If the density of an object is equal to the density of the fluid in which it is density of the fluid in which it is immersed, the object neither rises nor immersed, the object neither rises nor sinks in the fluid. sinks in the fluid.
- 12. Densities of Substances Densitiesof Substances
- 13. Densities of Substances Densitiesof Substances Changing the density of an object can Changing the density of an object can make it float or sink in a given fluid. For make it float or sink in a given fluid. For example, submarines change their example, submarines change their density by pumping water out of it’s density by pumping water out of it’s floatation tanks. The mass of the floatation tanks. The mass of the submarine decreases but the volume submarine decreases but the volume remains the same. remains the same.
- 14. Buoyancy and Density Buoyancyand Density Another way to change density is to Another way to change density is to change the volume. change the volume.
- 15. Ships Ships The shape ofa ship causes it to displace a The shape of a ship causes it to displace a greater volume of water than a solid greater volume of water than a solid piece of steel of the same mass. The piece of steel of the same mass. The greater the volume of water displaced, greater the volume of water displaced, the greater the buoyant force. A ship the greater the buoyant force. A ship stays afloat as long as the buoyant force stays afloat as long as the buoyant force is greater than its weight. is greater than its weight.