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Questions and Answers
What principle explains why a person can walk across deep, soft snow while wearing snowshoes?
What principle explains why a person can walk across deep, soft snow while wearing snowshoes?
Atmospheric pressure is exerted only by the air closest to the Earth's surface.
Atmospheric pressure is exerted only by the air closest to the Earth's surface.
False
What type of systems use liquids to transmit applied force?
What type of systems use liquids to transmit applied force?
Hydraulic systems
Increasing the temperature of a fluid will __________ its volume.
Increasing the temperature of a fluid will __________ its volume.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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What happens to the pressure of a fluid when its temperature increases?
What happens to the pressure of a fluid when its temperature increases?
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Compressors are used in pneumatic systems to decrease air pressure.
Compressors are used in pneumatic systems to decrease air pressure.
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What happens when an object's density is greater than the density of the fluid it is in?
What happens when an object's density is greater than the density of the fluid it is in?
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Balanced forces cause a change in the motion of an object.
Balanced forces cause a change in the motion of an object.
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Define buoyancy.
Define buoyancy.
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Pressure is calculated using the formula P = F / ______.
Pressure is calculated using the formula P = F / ______.
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What unit is used for measuring pressure?
What unit is used for measuring pressure?
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Match the following items with their corresponding properties:
Match the following items with their corresponding properties:
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What is the formula for calculating average density?
What is the formula for calculating average density?
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Unbalanced forces are equal in strength and cause no movement.
Unbalanced forces are equal in strength and cause no movement.
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Study Notes
Grade 8 Science Unit 3: Fluids & Viscosity - Chapter 9: Forces
- Forces influence the motion and properties of fluids.
Force
- Anything that causes a change in an object's motion.
- A push or a pull.
Balanced Forces
- Equal in strength.
- Opposite in direction.
- Result in no movement.
- Example: A person standing still on the Earth.
Unbalanced Forces
- Unequal in strength.
- Cause a change in speed or direction.
- Example: A child pushing down on one end of a seesaw.
Mass vs. Weight
-
Mass:
- Stays the same anywhere in the universe.
- Measured in kilograms (kg).
-
Weight:
- A measure of the push or pull acting on an object.
- Measured in Newtons (N).
- Weight varies based on the force of gravity. The same object weights differently on Earth, the moon and Jupiter.
Buoyancy
- The upward force on an object submerged in or floating on fluids.
- An object that floats has neutral buoyancy.
- The buoyant force is equal to the weight of the fluid that the object displaces.
Density & Buoyancy
- If the density of the immersed object is greater than the density of the fluid, it will sink.
Average Density
- The total mass of all substances that make up an object divided by the total volume.
Technologies Developed (based on fluids principles)
- Personal flotation devices.
- Submarines.
- Hot air balloons.
Pressure
- The force acting on a certain area of a surface.
- The larger the force, the greater the pressure.
- The smaller the area, the greater the pressure.
Calculating Pressure
- The unit for pressure is the Pascal (Pa).
- Pressure can be determined if force and area are known. - Formula: Pressure (P) = Force (F) / Area (A)
Sample Problems
- Provided example problems and solutions.
Determine Why
- Given specific examples: a person wearing snowshoes walking on deep snow and the variable flow of water coming out of a garden nozzle are studied.
Atmospheric Pressure
- Pressure exerted by the layers of air surrounding the Earth.
- Held by Earth's gravity (~160 km above Earth).
Pascal's Law
- Pressure applied to an enclosed fluid is transmitted equally throughout the entire container.
- Basis for hydraulic and pneumatic devices.
Hydraulics
- The study of pressure in liquids.
- Hydraulic systems are devices that transmit applied force through a liquid to move something else.
- Hydraulic systems use incompressible liquids.
- The pressure produced will exert in all directions equally.
Pneumatic Systems
- A gas is used to exert force on the gas in an enclosed space.
- Compressors are necessary as gases can be compressed to build up pressure.
Pressure & Volume
- Increasing pressure will decrease volume by the same amount.
- Known as Boyle's Law.
Temperature & Volume
- Increasing temperature will increase the volume of a fluid.
Temperature & Pressure
- Increasing temperature of a fluid will increase the pressure exerted.
Assignment
- Complete practice problems on pages 351-353.
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Description
Explore the essential principles of forces and their impact on fluids in this quiz based on Chapter 9 of Grade 8 Science. Understand concepts like balanced and unbalanced forces, as well as the difference between mass and weight. Test your knowledge on buoyancy and how these forces affect motion.
