Lesson 4-5 Flashcards
The mass per unit volume; the quantity of a matter into a unit volume of materials
Density
Relationship between the mass of the substance and how much volume it takes up
Density
The mass of atoms, their size, and how they are arranged determine the density of a substance
Density
The ratio of the oven-dry weight of wood to the weight of water with volume similar to that of the wood at specified moisture content.
Specific Gravity
The density of water w/ a temperature of ___/____ is commonly used as reference to compute SG.
4°C or 39°F
In computing the specific gravity of wood at various conditions, what is used as denominator?
volume of the wood
In computing the specific gravity what is used as numerator?
Oven dry weight
It is the material per unit volume.
Density
It is the ratio of the density of a substance to the density of a reference substance.
Specific gravity
What is the unit of density?
kg/m3 or g/cm3
What is the value of density?
Absolute value
What is the value of specific gravity?
Relative value
What is the nature of density?
A material has a unique value for density
What is the nature of specific gravity?
For solids and liquids, the ratio is measured using water as the reference substance. While for gases the ratio is measured using either hydrogen gas or normal air as the reference.
Reasons why we need to know specific gravity of wood and density?
Because it is an indicator of:
* Strength property
* Utilization value of wood
* Processing qualities of wood
* Measure of the amount of cell wall substances and the air spaces in the wood.
Regarded to be the most extensively used indicator of wood quality (Tesoro and Aday, 1990
Specific gravity
High specific gravity
=0.701 and above
Moderately high SG
= 0.601-0.700
Medium specific gravity
= 0.501-0.600
HSG Example
Molave
Yakal
Mangkono
Tindalo
Ipil
MHSG Example
Apitong
Guijo
Dao
Bagras
MSG Example
LTPA
Lauan
Tangile
Palosapis
Almaciga
What are the ways to determine SG?
- GRAVIMETRIC METHO
- FLOATATION METHOD
- MAXIMUM MC METHOD
- X-RAY DENSIOMETRY
METHOD
used to derive or determine the specific gravity of wood at various moisture contents when at least one specific gravity value at a certain moisture condition is given
BROWNE’S FORMULA
A method wherein the weight and volume of regular shaped wood are
considered.
GRAVIMETRIC METHOD
A method wherein the wood is allowed to float on water and submerge portion will
approximate the specific gravity.
FLOATATION METHOD
A method wherein the weight and volume of regular and irregular shaped wood.
MAXIMUM MC METHOD
A method wherein the wood is placed over the film and exposed to an x-ray and when the film is developed, then the specific gravity is determined.
X-RAY DENSIOMETRY
METHOD
_________ and _______ provide insights into the physical properties of wood, such as strength, hardness, and durability
Density and Specific Gravity
T/F Density is a dimensionless ratio that compares the density of a material to the density of water.
False
If wood has a specific gravity of ____ , it means its density equals that of water.
1.00
T/F Gravimetric method provides highly accurate measurements of wood density and non-destructive, preserving the integrity of
the wood sample for further analysis.
False
BUOY
To keep afloat
Buoyant
Capable of floating
The tendency of a body to float when submerged in a fluid or the power of a liquid to exert an upward force.
Buoyancy
It is the amount of force that is needed to push a piece of wood and float it in water.
Buoyant force of wood
Ability of a piece of wood to float due to buoyant force that develops as a result of the difference between the density of wood and water.
Buoyancy
General Rule of Buoyancy
The buoyant force is always present, whether the object floats, sinks, or is suspended in a fluid.
What if the buoyant force is greater than the object’s weight?
The object rises to the surface and floats.
What if the buoyant force is less than the object’s weight?
The object sinks.
What if the buoyant force equals the object’s weight?
The object can remain suspended at its present
depth
Weight ALWAYS acts _______. Buoyant Force (FB) always
acts ________.
downward, upward
It is equal to the weight of the fluid that is displaced
Buoyancy
Wood sinks if the density is
> 1g/cm3
Wood is neutrally buoyant if the density is
=1g/cm3
Wood floats if the density is
<1g/cm3
The _______ is equal to the weight of the fluid that is displaced
BF
Why ship float?
Because the weight of the ship is = to the Buoyant Force and Air-filled buoyancy chambers are built
What is the use of Air-filled buoyancy chambers?
makes the ship less dense than the volume of water it occupies, thus enabling it to float.
A principle that refers to the force of buoyancy that results when a body is submerged in a fluid, whether partially or
wholly.
ARCHIMEDES PRINCIPLE
Why does a body denser than water sinks?
because downward force due to the weight of the body is greater than the upward force
Factors affecting buoyancy
Volume of water displacement
Local Acceleration due to gravity
Density of water
