Unit A: Sections 3&4 (Grade 8) Flashcards
Density (P=rho), Viscosity, Pressure (Pa), Buoyancy, etc...
FLOW
What is flow?
How we describe FLUID (liquids & gases) movement.
- Fluids form a puddle, not a pile
- Movement is continuous and unbroken
- Individual particles can flow past one another
FLOW RATE
What is Flow Rate? What is it usually measured in?
The volume of a fluid flowing past a certain point, at a certain time.
- Flow rate decreases as viscosity increases
- Usually measured in L/s
HIGHER Viscosity = SLOWER Flow Rate
LOWER Viscosity = HIGHER Flow Rate
+Something about Planks Constant?
FRICTION
What is Friction?
Friction is a force that results when 2 objects rub or touch – CAUSES RESISTANCE
* If the 2 objects are rubbing/touching and go in opposite directions, it is resistance.
* If both object go the in the same direction, it is not resistance.
VISCOSITY
What is viscosity and what are the factors that influence it?
- How think/thin a fluid is
- HIGHER Resistance = MORE Viscous
- ~~The greater the rubbing between particles (friction) in any FLUID, the higher the viscosity. Fluids with a higher viscous. don’t flow as easily as fluids with low viscous.~~
-
OR A fluids viscosity is determined by it’s internal resistance.
What affects it: - Temperature
- Increasing temp = Decreasing viscosity // Decreasing temp. = Increasing Viscosity (- Think Kinetic Energy & Honey -)
-
Particle Type - some particles are more prone to resistance than others
*HIGHER Viscous = SLOWER Flow Rate (Usually Thicker)
LOWER Viscous = FASTER Flow Rate (Usually more Watery)
INTERNAL FRICTION
What is Internal Friction
An internal force that resists the movement between the particles of a material.
OR Friction that keeps a fluid from flowing
Simple – DENSITY
What is Density?
Simple Difinition: A property that describes how close together particles in matter are. More dense particles are crowded, whereas less dense particles have more room to move around in.
Scientific – DENSITY
Mass per Volume of a substance
MASS - Amount of matter measured in grams (g)
VOLUME - Amount of space occupied. (liquid = mL/ solid = cm3)
WATER
What is the density of water?
1g/mL
Sink or Float?
How would one determine if an object sinks of floats?
If the density of an object is higher than the density of the fluid ** it’s in, it will *SINK
If the density of an object is lower than the **density of the fluid ** it’s in, it will *FLOAT
—
If the buoyant force is greater than the gravitational force, the object will FLOAT
If the byuoyant force is weaker than the gravitational force the object will SINK
DENSITY – LIQUIDS & SOLIDS
What is the difference between units when measuring Liquids and Solids?
Liquids - g/mL or kg/L
Solids - g/cm3
CALCULATE DENSITY
How do we calculate density? What is P?
D = m/v
D = Density (example: 19.3 g/mL)
M = Mass (g/kg)
V = Volume (Liquids = mL/L, Solids = g/cm3)
p (for density) is greek for rho
Do the triangle method in emergencies
DENSITY + PARTICLE MODEL OF MATTER
Which states of matter are least/most dense? What affects density? Why?
- Different substances have different sized particles
- This can affect how many can ‘fit’ in a volume
- More space between particles the lower the density.
States of matter and their density: The more space between particles indicates a lower density. - Solids = More Dense
- Liquids = Moderate
- Gas = Least Dense
Exception: WATER
DENSITY & TEMPERATURE
As temperature increases, density decreases.
- As temp. increases, particles move faster
- As particles move faster, they move further apart
- As space increases between particles increases, density decreases.
Density does not change as long as the temperature stays consistent
SALT vs FRESH WATER
Are you most likely to float in salt or fresh water? Why?
Water on it’s own has the density of 1 g/mL.
Remember: density is affected by temperature, but also the partticles within it (concentration!).
Adding salt = adding particles (more particles = more mass)
Result: Density Increases
BUOYANCY
What is buoyancy?
The tendancy to float when placed in a fluid.
NOTE: There are always 2 Forces acting upon an object when in a fluid:
- Gravity: Pushes DOWN on an object (of the gravity is greater than the buoyant force, the object will SINK)
- Buoyant Force: Pushes UP on an object (if the buoyant force on an object is greater than the gravity, the object will FLOAT)
Examples of Buoyancy
What are some applicants of buoyancy we use in our daily lives?
- Buoy
- Ship
- etc…
COMPRESSIBILITY
What is compressibility?
When a force pushes on an object, the object is said to be under compression. Objects under compression tend to deform in shape.
Think of kicking a soccer ball, your foot is compressing the fluid (air) within the ball
COMPRESSION – GASES vs LIQUIDS
Is it easier to compress an empty bottle or one filled with water?
The empty one!
Gases can be compressed more than liquids because gases have more space to waste.
Expand? In a gas, there are less particles so they have space to be compressed.
Liquids however, are said to be INCOMPRESSIBLE. - Liquid particles don’t have anywhere to go
Think of the pistons in science class with Ms. Johnson
Higher Volume = Low Pressure – High Pressure = Smaller Volume
Pressure
What is pressure?
Pressure is the amount of force aplied to a given area.
More Force = More Pressure
Area Increases = Pressure Decreases
Area Decreases = Pressure Increases
Think: What hurts more? Being punched hard or soft?
Blaise Pascal
Who was this guy?
Simple Definition: An intelligent mathematician who originated from the 1600s. He created the concept of pressure. His name was Pascal
In-Depth Definition: Blaise Pascal was a French Mathematician who was curious about fluids and preformed some experiments.
Calculate Pressure
P = F/A
P = Pressure (Pa)
F = Force (N)
A = Area (~m2)
(~) is usually
Pressure - Water Bottle & The 3 holes
You have a water bottle with 3 holes. One at the top, bottom, and one in the middle. Where will the water come out with more pressure?
A: The bottom hole.
Why? The water lower down has all the weight of the water above pushing down on it. In other words: it has more force pushing it down
More force = more pressure
Greater depth = greater pressure
Pascal’s Law
What was Pascal’s Law
Pressure applied to a fluid in a closed system will be transmitted throughout the fluid at the same strength.
Pressure will push on all sides of the container at right angles.
Hydraulic Devices
What is a hydraulic device?
A hydraulic device uses LIQUID
- Uses 2 pistons of different sizes
- Small piston = input (pushes down on liquid to create pressure)
- The pressure is transmitted through the liquid and pushes up on the large piston
- Big Piston = output
- The big piston has a much larger area, but, the pressure is the same throughout the whole system.