SOUND
The definition of sound
Sound is a longitudinal wave which spreads in the from of compression and rarefaction.
Sound is produced by an oscillation of matter.
Sound, which is produced by a vibrating object (source of sound), spreads out in air in the form of a longitudinal wave.
If you hit a drum, the membrane of the drum will vibrate. The air molecules surrounding the drum vibrate too, and longitudinal waves spread out to all directions. If the waves reach your ears, you will hear the sound of the drum.
Sound energy can spread out in solids, liquids, and gases (such as, wood, glass, steel, water, and air). Therefore, sound needs a medium. Without a medium to spread out, the sound will not occur.
On the surface of the moon there is no atmosphere, so there is no medium to spread out sound waves.
The sound of the electric bell which is placed in the bell jar can still be heard because there is air in the jar. After the air in the jar is pumped out, there is a vacuum, so the sound of the electric bell cannot be heard. This shows that sound cannot spread out in a vacuum.
So, we can hear a sound if there is a sound source and a medium that transmits the sound from its source to our ears.
Speed of sound depends on two things:
1. temperature of medium
2. kind of medium( solid, liquid and gas )
Air is a medium that is most often passed by sound waves. Sound can spread out through different kinds of media. Liquids and solids are better media than air because the particles in liquids or solids produce stronger interaction than the particles of air do. This causes the movement of sound waves in solids and liquids to be easier than in air.
In the rainy season, we often see a flash of lightning followed by a sound of thunder within a few seconds. This happens because the position of the lightning is far from you. Actually, the flash of lightning and the sound of thunder occur at the same time. But, you hear the sound of the thunder after you have seen the flash. This is fact indicates that the speed of light is faster than the speed of sound. Light travels at the speed of 300,000,000 m/s in a vacuum while the speed of sound is 330 m/s.
The speed of sound in the air depends on its temperature. The higher the temperature of the air, the faster the speed of sound, and vice versa.
The speed of sound can be formulated :
v= s/t
Note : v = the speed of sound ( m/s )
s = distance ( m)
t = time (s )
Rabu, 29 Juli 2009
RESUME PHYSIC SEMESTER GASAL
CHAPTER I MEASUREMENT
A. Definition of Measurement
Measuring is to compare a physical quantity of an object with similar quantity used as a unit.
Measuring systems :
1. The British system : gallon for water
Yard for thread
Inch for pipe
2.Since 1700 some scientists have used measuring system is called The metric system.
In 1960 the metric system was used and officially called the international system or SI units.
QUANTITIES AND UNITS
a physical quantity is a quantity which can be measured. Such as length, mass, and so on.
The quantity which cannot be measured is not a physical quantity such as sadness, love and loyalty.
The physical quantity is divided into : fundamental quantity and derived quantity .
The fundamental quantities are the quantities that has been defined their own units.
In 1971 the international system uses the 7 fundamental quantities as follows :
Fundamental quantities : Length( m )
Mass ( kg )
Time ( s )
Temperature ( kelvin = K )
Luminous Intensity ( Candela =Cd)
Amount of substance ( Mole = mol)
Electric current ( ampere = A )
Derived quantities are the quantities that derived from these fundamental quantities.
such as : volume,density,velocity,force,work and so on.
I. LENGTH
Length represents the distance between two points.
Length uses SI unit in meter ( m ). One standard meter is the same as the distance
traveled by light in a vacuum in 1/ 299.792.458 second
some tools for measuring length :
a. ruler.
b. a meter tape
c. vernier caliper.( jangka sorong )
d. srew micrometer ( micrometer skrup )
II. MASS
Every substance consists of materials.
Mass is the amount of materials in the substance.
Mass is not the same as weight.
The mass of an object is determined by the contained materials in it , and it is fixed although the objects position changes.
Weight depends on the position of the object on the earth and is affected by the gravitational force.
In SI, mass uses basic unit kilogram ( kg ),while weight is Newton ( N ).
The mass of an object is measured with lever balance or balance
Weight is measured with spring balance/ dynanometer
III. TIME
Time is the duration between two events.
The SI unit for time is second ( s).
One standard second is the time needed by Cesium atom to vibrate 9,172,631,770 times.
For long events, time is stated in larger units such as minute, hour , day, year, centaury , etc. But for a fast event, you can use millisecond ( ms ), microsecond (μs), and nanosecond ( ns ).
II. TEMPERATURE
The temperature is the degree of hotness and coldness of an object.
The tool for temperature is a thermometer.
Unit of temperature in SI unit is Kelvin
CHAPTER I MEASUREMENT
A. Definition of Measurement
Measuring is to compare a physical quantity of an object with similar quantity used as a unit.
Measuring systems :
1. The British system : gallon for water
Yard for thread
Inch for pipe
2.Since 1700 some scientists have used measuring system is called The metric system.
In 1960 the metric system was used and officially called the international system or SI units.
QUANTITIES AND UNITS
a physical quantity is a quantity which can be measured. Such as length, mass, and so on.
The quantity which cannot be measured is not a physical quantity such as sadness, love and loyalty.
The physical quantity is divided into : fundamental quantity and derived quantity .
The fundamental quantities are the quantities that has been defined their own units.
In 1971 the international system uses the 7 fundamental quantities as follows :
Fundamental quantities : Length( m )
Mass ( kg )
Time ( s )
Temperature ( kelvin = K )
Luminous Intensity ( Candela =Cd)
Amount of substance ( Mole = mol)
Electric current ( ampere = A )
Derived quantities are the quantities that derived from these fundamental quantities.
such as : volume,density,velocity,force,work and so on.
I. LENGTH
Length represents the distance between two points.
Length uses SI unit in meter ( m ). One standard meter is the same as the distance
traveled by light in a vacuum in 1/ 299.792.458 second
some tools for measuring length :
a. ruler.
b. a meter tape
c. vernier caliper.( jangka sorong )
d. srew micrometer ( micrometer skrup )
II. MASS
Every substance consists of materials.
Mass is the amount of materials in the substance.
Mass is not the same as weight.
The mass of an object is determined by the contained materials in it , and it is fixed although the objects position changes.
Weight depends on the position of the object on the earth and is affected by the gravitational force.
In SI, mass uses basic unit kilogram ( kg ),while weight is Newton ( N ).
The mass of an object is measured with lever balance or balance
Weight is measured with spring balance/ dynanometer
III. TIME
Time is the duration between two events.
The SI unit for time is second ( s).
One standard second is the time needed by Cesium atom to vibrate 9,172,631,770 times.
For long events, time is stated in larger units such as minute, hour , day, year, centaury , etc. But for a fast event, you can use millisecond ( ms ), microsecond (μs), and nanosecond ( ns ).
II. TEMPERATURE
The temperature is the degree of hotness and coldness of an object.
The tool for temperature is a thermometer.
Unit of temperature in SI unit is Kelvin
Minggu, 12 Juli 2009
RESUME CHAPTER 1 FORCE
RESUME SEMESTER GASAL PHYSIC VIII
FORCE
The definition of force
Force is a push or pull.
The force can causes change as follows :
1. an object at rest become moving
2. the moving an object to be at rest
3. the directions of an object
4. the shape and size
5. the velocity
Types of force
1.Contact forces
Contact forces is the force which happen because of the presence of a touch between two or more things
Example : muscle or muscular force, friction force, machine
force, spring force.
2.Non contact forces
Non contact force is force which happen without contact with the another thing
Example : gravitational force, electric force, magnetic force
DRAWING AND MEASURING A FORCE
The device used to measure force is spring balance or dynamometer
In SI, Force is measured in unit of Newton( N ) and in CGS system, force is measured in unit dyne.
1 N = 105 dyne
N = kgm/s2
Dyne = gr/cm2
The force is vector quantity because force has value and direction.
The force can be drawn by using a diagram vector in the form of an arrow, as the figure below:
The direction of force is represented by direction of arrow
The magnitude of force is represented by the length of arrow
RESULTANT FORCE
1.
R= F1 + F2, if two force the same direction
2.
R= F1- F2 , if two force the opposite direction
3. F1
F2
If two force the perpendicularly direction
R =
Friction force
Do you ever walk on the slippery floor then you walk on the rough floor ?do you feel the difference ?
Friction force is the force produced because of direct contact between two bodies surface.
The direction of friction force is opposite direction with direction of bodies motion.
fs F
Friction force is divided into two kinds ,those are :
1. static friction force ( fs ) ,namely a friction force between two bodies that will start to move or at rest.
2. kinetic friction ( fk ),namely a friction force between two bodies which one of the body moves.
Beneficial friction force:
1.friction force between feet and surface of floor cause we can walk
2.friction force between parachute and air cause the parachute can fly on the air and fall slowly.
3. braking system in a vehicle to retard/stop the vehicle.
4. friction force between car tires which is made serrated so the car is not slipped
Harmful friction force :
1. friction force between car /motorcycle tires and road cause car /motorcycle tires are quickly thin
2. friction force piston and cylinder in car engine so the engine hot quickly which cause it timeworn quickly.
3. friction force between air and the body of motorcycle rider, causes the motion of
motorcycle is retarded
4. the base of sandal become thin because often in friction with the road.
WEIGHT
The weight of an object is defined as the gravitational force acting on the mass of an object.
W = m.g
Note : w = weight (N )
m = mass ( kg )
g = gravitational acceleration ( m/s2 = N/kg )
weight of an object can change depends on the magnitude of gravitational force.
Weight can be measured with a spring balance
Mass is the amount of materials in the substance. It is constants everywhere in the universe.
Exercise :
A boy has a mass of 45 kg.what is his weight (a) on earth ( b) on the moon ? take g= 10 ms-2 and the acceleration due to gravity on the moon to be one sixth its value on earth .
NEWTON’S LAWS
Newton’s I Law explaines :
Σ F = 0Every body will be at rest or moves in uniform rectilinear if there is no force change that condition.
Formula Newton’s I law =
The property to stand self condition is called as inertia. So Newton’s I law or as inertia law.
Newton’s II Law explaines :
The acceleration of object which is caused by force is directly proportional to the magnitude of force and inversely proportional to its mass.
Formula Newton’s II law =
a =
a = acceleration ( m/s2 )
F = force ( N )
m = mass (kg )
Newton’s III Law explaines :
If the first object makes force ( making action) to second object, appears reaction force from the second object to first object which the directions are in opposite.
Formula Newton’s III Law = F action = - F reaction or F1 = -F2
Archimedes’ Law
“ an object which is immersed partly or entirely into liquid, will get lift force which the magnitude is equal to the weight of liquid moved by the object.
Mathematically ,Archimedes law is formulated as follows
Fa = ρ. g.V Fa = wu - waNote : Fa = Lift force ( N )ρ = Density of liquid ( kg/m3 )
g = gravitational acceleration (m/s2)
V = volume of object ( m3 )
wu = weight in air ( N )
wa = weight in liquid ( N )
Floating , suspending , Sinking
Fa Fa Fa
W W W
Energy and Work
a. Energy
Energy is the ability to make changes.
Energy is the ability to do work.
Forms of energy :
1. potential energy
2. kinetic energy
3. mechanic energy
4. heat energy
5. sound energy
6. light energy
7.
Energy always changes from one form to another.
FORCE
The definition of force
Force is a push or pull.
The force can causes change as follows :
1. an object at rest become moving
2. the moving an object to be at rest
3. the directions of an object
4. the shape and size
5. the velocity
Types of force
1.Contact forces
Contact forces is the force which happen because of the presence of a touch between two or more things
Example : muscle or muscular force, friction force, machine
force, spring force.
2.Non contact forces
Non contact force is force which happen without contact with the another thing
Example : gravitational force, electric force, magnetic force
DRAWING AND MEASURING A FORCE
The device used to measure force is spring balance or dynamometer
In SI, Force is measured in unit of Newton( N ) and in CGS system, force is measured in unit dyne.
1 N = 105 dyne
N = kgm/s2
Dyne = gr/cm2
The force is vector quantity because force has value and direction.
The force can be drawn by using a diagram vector in the form of an arrow, as the figure below:
The direction of force is represented by direction of arrow
The magnitude of force is represented by the length of arrow
RESULTANT FORCE
1.
R= F1 + F2, if two force the same direction
2.
R= F1- F2 , if two force the opposite direction
3. F1
F2
If two force the perpendicularly direction
R =
Friction force
Do you ever walk on the slippery floor then you walk on the rough floor ?do you feel the difference ?
Friction force is the force produced because of direct contact between two bodies surface.
The direction of friction force is opposite direction with direction of bodies motion.
fs F
Friction force is divided into two kinds ,those are :
1. static friction force ( fs ) ,namely a friction force between two bodies that will start to move or at rest.
2. kinetic friction ( fk ),namely a friction force between two bodies which one of the body moves.
Beneficial friction force:
1.friction force between feet and surface of floor cause we can walk
2.friction force between parachute and air cause the parachute can fly on the air and fall slowly.
3. braking system in a vehicle to retard/stop the vehicle.
4. friction force between car tires which is made serrated so the car is not slipped
Harmful friction force :
1. friction force between car /motorcycle tires and road cause car /motorcycle tires are quickly thin
2. friction force piston and cylinder in car engine so the engine hot quickly which cause it timeworn quickly.
3. friction force between air and the body of motorcycle rider, causes the motion of
motorcycle is retarded
4. the base of sandal become thin because often in friction with the road.
WEIGHT
The weight of an object is defined as the gravitational force acting on the mass of an object.
W = m.g
Note : w = weight (N )
m = mass ( kg )
g = gravitational acceleration ( m/s2 = N/kg )
weight of an object can change depends on the magnitude of gravitational force.
Weight can be measured with a spring balance
Mass is the amount of materials in the substance. It is constants everywhere in the universe.
Exercise :
A boy has a mass of 45 kg.what is his weight (a) on earth ( b) on the moon ? take g= 10 ms-2 and the acceleration due to gravity on the moon to be one sixth its value on earth .
NEWTON’S LAWS
Newton’s I Law explaines :
Σ F = 0Every body will be at rest or moves in uniform rectilinear if there is no force change that condition.
Formula Newton’s I law =
The property to stand self condition is called as inertia. So Newton’s I law or as inertia law.
Newton’s II Law explaines :
The acceleration of object which is caused by force is directly proportional to the magnitude of force and inversely proportional to its mass.
Formula Newton’s II law =
a =
a = acceleration ( m/s2 )
F = force ( N )
m = mass (kg )
Newton’s III Law explaines :
If the first object makes force ( making action) to second object, appears reaction force from the second object to first object which the directions are in opposite.
Formula Newton’s III Law = F action = - F reaction or F1 = -F2
Archimedes’ Law
“ an object which is immersed partly or entirely into liquid, will get lift force which the magnitude is equal to the weight of liquid moved by the object.
Mathematically ,Archimedes law is formulated as follows
Fa = ρ. g.V Fa = wu - waNote : Fa = Lift force ( N )ρ = Density of liquid ( kg/m3 )
g = gravitational acceleration (m/s2)
V = volume of object ( m3 )
wu = weight in air ( N )
wa = weight in liquid ( N )
Floating , suspending , Sinking
Fa Fa Fa
W W W
Energy and Work
a. Energy
Energy is the ability to make changes.
Energy is the ability to do work.
Forms of energy :
1. potential energy
2. kinetic energy
3. mechanic energy
4. heat energy
5. sound energy
6. light energy
7.
Energy always changes from one form to another.
Minggu, 05 Juli 2009
Pressure
RESUME
Competence Standard :3.To understand the concept of motion,work,force and energy in daily life.
Basic Competence : 3.5. To investigate the pressure at solid,liquid and gas and their application in daily life.
Material : Pressure
Pressure is defined as force acting on a unit area.
A. Solid pressure
Solid pressure is defined as force acting on a unit area.
The formula of solid pressure
P =
Notice : P = Pressure ( N/m2)
F = Force ( N )
A = Area ( m2 )
B. Fluid Pressure
- Fluids are substances that do not have fixed shapes. Liquids and gas belong
to fluids.
- Because of gravitation, pressure in fluids increases with the increase of the
fluid depth
- Fluids move from higher-pressure areas to lower-pressure areas.
- Liquid pressure ( Hydrostatic Pressure ) P = ρ .g . h
- Pascal’s principle states that pressure applied to an enclosed liquid is
transmitted equally to every part of the liquid.
- Several device that work according to Pascal’s prinsiple :
Hydraulic jack
Hydraulic press
Hydraulic brake
Car lifter device
- Connected vessel
- If the connected vessel is filled by the same liquid and in balance condition liquid surface in the vessel is located on one flat plane.
- Connected vessel doesn’t hold if :
1. the vessel is filled with more than one kind of liquid
2. the vessel is in closed condition
3. there is capillary pipe.
- Archimedes’s principle states that the buoyancy force working on an object in a fluid is equal to the fluid weight moved by the object.
Fa = ρ . g . v
Fa = wu - wa
Notice :
Fa = buoyancy force ( N )
ρ = density of liquid ( kgm-3 )
g = gravitational acceleration ( ms-2)
V = volume ( m3)
Floating , suspending , Sinking
Fa Fa Fa
W W W
Floating : W = Fa
ρo < ρf
Suspending : W = Fa
ρo =ρf
Sinking : W > Fa
ρo > ρf
Air Pressure
1. Atmospheric pressure above sea level is 101,300 Pa or 760 mmHg or 1 atmosphere. The higher the altitude, the lower the air pressure.
2. An instrument for measuring the atmospheric pressure is a barometer, whereas an instrument for measuring air pressure in a closed compartment is a manometer.
3. Boyle’s law states that if the gas volume decreases, the pressure increases at a constant temperature.
P x V = C
P1. V1 = P2 . V2
4. Charles law states that the gas volume increases if the temperature increases at a constant pressure.
Competence Standard :3.To understand the concept of motion,work,force and energy in daily life.
Basic Competence : 3.5. To investigate the pressure at solid,liquid and gas and their application in daily life.
Material : Pressure
Pressure is defined as force acting on a unit area.
A. Solid pressure
Solid pressure is defined as force acting on a unit area.
The formula of solid pressure
P =
Notice : P = Pressure ( N/m2)
F = Force ( N )
A = Area ( m2 )
B. Fluid Pressure
- Fluids are substances that do not have fixed shapes. Liquids and gas belong
to fluids.
- Because of gravitation, pressure in fluids increases with the increase of the
fluid depth
- Fluids move from higher-pressure areas to lower-pressure areas.
- Liquid pressure ( Hydrostatic Pressure ) P = ρ .g . h
- Pascal’s principle states that pressure applied to an enclosed liquid is
transmitted equally to every part of the liquid.
- Several device that work according to Pascal’s prinsiple :
Hydraulic jack
Hydraulic press
Hydraulic brake
Car lifter device
- Connected vessel
- If the connected vessel is filled by the same liquid and in balance condition liquid surface in the vessel is located on one flat plane.
- Connected vessel doesn’t hold if :
1. the vessel is filled with more than one kind of liquid
2. the vessel is in closed condition
3. there is capillary pipe.
- Archimedes’s principle states that the buoyancy force working on an object in a fluid is equal to the fluid weight moved by the object.
Fa = ρ . g . v
Fa = wu - wa
Notice :
Fa = buoyancy force ( N )
ρ = density of liquid ( kgm-3 )
g = gravitational acceleration ( ms-2)
V = volume ( m3)
Floating , suspending , Sinking
Fa Fa Fa
W W W
Floating : W = Fa
ρo < ρf
Suspending : W = Fa
ρo =ρf
Sinking : W > Fa
ρo > ρf
Air Pressure
1. Atmospheric pressure above sea level is 101,300 Pa or 760 mmHg or 1 atmosphere. The higher the altitude, the lower the air pressure.
2. An instrument for measuring the atmospheric pressure is a barometer, whereas an instrument for measuring air pressure in a closed compartment is a manometer.
3. Boyle’s law states that if the gas volume decreases, the pressure increases at a constant temperature.
P x V = C
P1. V1 = P2 . V2
4. Charles law states that the gas volume increases if the temperature increases at a constant pressure.
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