Grade 8 Science Unit 3: Fluids and Viscosity

Fluids and Viscosity

• Grade 8 Science Unit 3 explores fluids and viscosity.
• Chapter 9 focuses on how forces affect fluid motion and properties.

Force

• A force is anything changing an object's motion.
• A force can be a push or a pull.

Balanced Forces

• Balanced forces have equal strength and opposite directions.
• Balanced forces cause no movement changes.

Unbalanced Forces

• Unbalanced forces have unequal strength.
• Unbalanced forces cause changes in speed or direction.

Mass vs. Weight

• Mass: Stays constant anywhere in the universe, measured in kilograms (kg).
• Weight: Measures the push or pull on an object, measured in Newtons (N).
  • Weight varies based on gravity.

Buoyancy

• Buoyancy is the upward force on an object submerged or floating in a fluid.
• An object floating has neutral buoyancy.
• The buoyant force equals the weight of the displaced fluid.

Density and Buoyancy

• An object sinks if its density is greater than the fluid's density.

Average Density

• Average density is the total mass of an object divided by its total volume.

Technologies Developed

• Personal flotation devices.
• Submarines.
• Hot air balloons.

Pressure

• Pressure is the force acting on a surface area.
• Pressure increases with larger forces and smaller areas.
• The unit of pressure is the Pascal (Pa).

Calculating Pressure

• Pressure (P) equals Force (F) divided by Area (A).

Sample Problems

• Various sample problems and calculations related to pressure, force, and area of objects immersed or floating in fluids.

Atmospheric Pressure

• Atmospheric pressure is the pressure exerted by the Earth's atmosphere.

Pascal's Law

• Pressure applied to a closed fluid is transmitted equally throughout the container.
• Pascal's Law is the basis for hydraulic and pneumatic devices.

Hydraulics

• Hydraulics is the study of pressure in liquids.
• Hydraulic systems use liquids to transmit force through liquids and move something else.
• Liquids are incompressible, so they are ideal for hydraulic systems.

Pneumatic Systems

• Pneumatic systems use gases to exert force on enclosed spaces.
• Compressors are utilized to compress gases and build up air pressure.

Pressure & Volume

• Increasing fluid pressure decreases volume proportionally (Boyle's Law).

Temperature & Volume

• Increasing fluid temperature increases volume.

Temperature & Pressure

• Increasing fluid temperature increases pressure.

Assignment

• Practice problems on pages 351-353.