Section 1: Fluids and pressure
Vocabulary
1) Fluid: a nonsolid state of matter in which the atoms or molecules are free to move past each other, as in a gas or liquid
2) Pressure: the amount of force exerted per unit area of a surface
3) Pascal: the SI unit of pressure (symbol, Pa)
4) Atmospheric Pressure: the pressure caused by the weight of the atmosphere
2) Pressure: the amount of force exerted per unit area of a surface
3) Pascal: the SI unit of pressure (symbol, Pa)
4) Atmospheric Pressure: the pressure caused by the weight of the atmosphere
section summary
Section 2: buoyant force
vocabulary
1) Buoyant Force: the upward force that keeps an object immersed in or floating on a liquid
2) Archimedes' Principle: the principle that states that the buoyant force on an object in a fluid is an upward force equal to the weight of the volume of fluid that the object displaces.
2) Archimedes' Principle: the principle that states that the buoyant force on an object in a fluid is an upward force equal to the weight of the volume of fluid that the object displaces.
section summary
This section discussed buoyant force (vocabulary word 1) which is the upward force fluids exert on all matter. Buoyant force can be determined by archimedes' principle (vocabulary word 2) which states that the buoyant force on an object in a fluid is an upward force equal to the weight of the volume of fluid that the object displaces. An object sinks when its weight is greater than the buoyant force (Ex: a 75 N rock sinking in water with a buoyant force of 50 N). An object floats when the weight of the object is equal to the buoyant force of the fluid it is in (Ex: a 9 N duck floating in water with a buoyant force of 9 N.). Also, when the buoyant force of a fluid is greater than the objects weight then the object buoyed up (push up). You may have experienced this when trying to jump into a pool with a floatie on and being pushed to the surface of the water. An object is buoyed up until the part of the object underwater displaces an amount of water that equals the objects entire weight. This is also why ice pops up after a sinking to the bottom of water.
Density also effects whether an object sinks or floats. If the density of the object is greater than the fluid that its in, then the object will sink. If the density of the object is less than the fluid that it is in, then it will float. For example, when you release a rock it "sinks" in the air because it is more dense than the air. Also, helium is used in balloons because helium is less dense than air so it causes balloons to float. Overall density however can be changed to allow certain objects to float. For example, a solid block of lead would sink when placed in water, but if it is then shaped into a hollow form then it would float because there is less mass in a greater volume. Ships are made this way so that they don't sink. Submarines also use a similar method to navigate waters. In order ]to float partially on the surface of water, submarines fill their ballast tanks mostly with air. To cause the submarine to sink further in the water, it fills its ballast tanks with water to add to its mass (which increases its overall density) and causes it to sink. When the submarine wants to resurface it simply adds compressed air from vent holes to the ballast tanks. This then pushes the water out and decreases its overall mass and decreases its overall density (allowing it to resurface). Fish use their swim bladders in a similar fashion to either increase or decrease its volume. The change in volume will either increase or decrease its overall density which will allow it to either sink further or float up further.
Density also effects whether an object sinks or floats. If the density of the object is greater than the fluid that its in, then the object will sink. If the density of the object is less than the fluid that it is in, then it will float. For example, when you release a rock it "sinks" in the air because it is more dense than the air. Also, helium is used in balloons because helium is less dense than air so it causes balloons to float. Overall density however can be changed to allow certain objects to float. For example, a solid block of lead would sink when placed in water, but if it is then shaped into a hollow form then it would float because there is less mass in a greater volume. Ships are made this way so that they don't sink. Submarines also use a similar method to navigate waters. In order ]to float partially on the surface of water, submarines fill their ballast tanks mostly with air. To cause the submarine to sink further in the water, it fills its ballast tanks with water to add to its mass (which increases its overall density) and causes it to sink. When the submarine wants to resurface it simply adds compressed air from vent holes to the ballast tanks. This then pushes the water out and decreases its overall mass and decreases its overall density (allowing it to resurface). Fish use their swim bladders in a similar fashion to either increase or decrease its volume. The change in volume will either increase or decrease its overall density which will allow it to either sink further or float up further.
Helpful Site Just A Click Away! Buoyant Force
section 3: Fluids in motion
vocabulary
1) Bernoulli's Principle: the principle that states that the pressure in a fluid decreases as the fluid's velocity increases
2) Lift: an upward force on an object that moves in a fluid
3) Thrust: the pushing or pulling force exerted by the engine of an aircraft or rocket
4) Drag: a force parallel to the velocity of the flow; it opposes the direction of an aircraft and, in combination with thrust, determines the speed of the aircraft
5) Pascal's Principle: the principle that states that a fluid in equilibrium contained in a vessel exerts a pressure of equal intensity in all directions
2) Lift: an upward force on an object that moves in a fluid
3) Thrust: the pushing or pulling force exerted by the engine of an aircraft or rocket
4) Drag: a force parallel to the velocity of the flow; it opposes the direction of an aircraft and, in combination with thrust, determines the speed of the aircraft
5) Pascal's Principle: the principle that states that a fluid in equilibrium contained in a vessel exerts a pressure of equal intensity in all directions
section summary
This section discussed fluids in motion. Bernoulli's principle helps describe the relationship between fluid speed and pressure. Bernoulli's principle (vocabulary word 1) states that the pressure in a fluid decreases as the fluid's velocity increases. This principle also helps explain how planes gain lift. Lift (vocabulary word 2) is an upward force on an object that moves in a fluid. According to Bernoulli's principle, the fast-moving air above the wing exerts less pressure than the slow-moving air below the wing, which causes the greater pressure below the wing to exert an upward force. Lift is also effected by thrust (vocabulary word 3) which is the pushing or pulling force exerted by the engine of an aircraft or rocket. Generally, a plane with a large large amount of thrust moves faster than a plane that has less thrust does. This is due to air traveling around the wing at higher speeds, which increases lift. Wing size also determines how much thrust is needed to get a certain amount of lift. For example, jets have small wings but gain lift because they have powerful engines that create a large amount of thrust. Gliders on the other hand have large wings and no engine but gain lift because their wings cover a large surface area, which allows them to glide on air.
Next is drag and fluid motion. All fluids exert a force that opposes the motion of objects in the fluid. This force is called drag (vocabulary word 4). For example, drag working against a plane is usually caused by an irregular unpredictable flow of air, turbulence. When drag causes turbulence and reduces the lift of planes, they can adjust the flaps on the wings to change the shape or area of the wing and reduce drag (and increase lift).
Lastly is Pascals principle. Pascals principle (vocabulary word 5) states that a fluid in equilibrium contained in a vessel exerts a pressure of equal intensity in all directions. Hydraulic devices use pascals principle to move or lift objects. They can can also multiply forces. Liquids are used in hydraulic devices because liquids cannot be easily compressed. Cranes, forklifts, and bulldozers have hydraulic devices that help them lift heavy objects.
Next is drag and fluid motion. All fluids exert a force that opposes the motion of objects in the fluid. This force is called drag (vocabulary word 4). For example, drag working against a plane is usually caused by an irregular unpredictable flow of air, turbulence. When drag causes turbulence and reduces the lift of planes, they can adjust the flaps on the wings to change the shape or area of the wing and reduce drag (and increase lift).
Lastly is Pascals principle. Pascals principle (vocabulary word 5) states that a fluid in equilibrium contained in a vessel exerts a pressure of equal intensity in all directions. Hydraulic devices use pascals principle to move or lift objects. They can can also multiply forces. Liquids are used in hydraulic devices because liquids cannot be easily compressed. Cranes, forklifts, and bulldozers have hydraulic devices that help them lift heavy objects.