Grade 8 Science Unit 3: Fluids & Viscosity

Grade 8 Science Unit 3: Fluids & Viscosity

• This unit covers forces influencing fluid motion and properties.

Chapter 9: Forces Affecting Fluids

• Forces cause changes in the motion of objects.
• Forces can be pushes or pulls.

Balanced Forces

• Balanced forces are equal in strength and opposite in direction.
• Balanced forces result in no movement.

Unbalanced Forces

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

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).

Buoyancy

• The upward force on an object submerged in or floating on fluids.
• An object that floats has neutral buoyancy.
• The buoyant force equals the weight of the fluid displaced by the object.

Density & Buoyancy

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

Average Density

• Calculated by dividing the total mass of an object by its total volume.

Technologies Developed

• Personal flotation devices
• Submarines
• Hot air balloons

Pressure

• Pressure is the force acting on a certain area of a surface.
• Larger force means greater pressure.
• Smaller area means greater pressure.
• Unit for pressure is the Pascal (Pa).

Calculating Pressure

• Pressure (P) = Force (F) / Area (A)

Sample Problems

• Example calculation 1: Determine the pressure exerted by water on the base of an aquarium. Given weight of water and area of the base.
• Example calculation 2: Determine the force exerted by atmospheric pressure on a hand. Example given atmospheric pressure and palm area.
• Example calculation 3: Determine the area of the bottom of a glass given the weight of water and the water pressure on the base.

Determining Why...

• Snowshoes: Allow people to walk on deep, soft snow without sinking by increasing the area over which the person's weight is distributed.
• Garden Hose Nozzle: Allows for control of water flow speed by varying the area of the water jet.

Atmospheric Pressure

• The pressure exerted by air layers around Earth held by gravity.

Pascal's Law

• Pressure applied to an enclosed fluid transmits equally throughout the container.
• Basis for hydraulic and pneumatic devices.

Hydraulics

• The study of pressure in liquids.
• Hydraulic systems transmit applied force through a liquid to move something else.

Hydraulic Systems

• Use liquids because they are incompressible
• Enclosed in tubes or pipes
• Pressure exerted equally in all directions

Pneumatic Systems

• Use gases to exert a force in enclosed spaces.
• Compressors are necessary as gases are compressible; they increase the pressure of gases

Pressure & Volume (Boyle's Law)

• Increasing pressure of a fluid decreases volume by the same amount.

Temperature & Volume

• Increasing temperature increases fluid volume.

Temperature & Pressure

• Increasing temperature increases fluid pressure.

Assignment

• Complete practice problems on pages 351-353.

Explore the concepts of fluids and viscosity in this quiz covering balanced and unbalanced forces, mass vs. weight, and buoyancy. Test your understanding of how these principles affect fluid motion and properties. Perfect for Grade 8 students learning about the forces that influence fluid behavior.