Lesson one: Types of levers
The most common simple machines are levers.
The lever: is a rigid bar that rotates around a fixed point called the fulcrum and is affected by effort force and resistance force.
Levers were first described in the year 260 B.C by the Greek scientist (Archimedes)
Fulcrum: A fixed point on which a solid bar is placed.
Importance of the levers:
1- Increase force by save the effort exerted by using small force to move heavy load like crowbar and nutcracker
G.R The crowbar is considered as force lever (save effort).
Because it used to make a great effort by using a small force
2- Increase distance by exerting a force for a small distance to move object large distance like the broom
3- Increase speed of object that affect on as in the hockey batمضرب الهوكي
4- Moving force from place to another like in manual broom.
5- accuracy in performance like using the tweezers to pick up very small objects
6- Avoid dangers like heat, cold and poisonous materials as in coal holder
Types of levers:
First class Second class Third class
Middle point Fulcrum Force of resistance Force of effort
Examples See-sawالارجوحه
Crowbar العتله
Scissors المقص
Suction pump مضخة ماء
Paddle مجداف
Nail clipper قصافة
Pincer كماشة
Pliers زردية
Balance Nutcracker
Soda-water opener
Wheel barrow
Stapler دباسة Fish tool
Manual broom
Sweat – ice –coal holder
Tweezers ملقاط
Hockey bat مضرب
Claw hammer خلاعة مسامير
Exercises
Write the scientific term:
1-The fixed point of a rigid bar rotate on.
2- A rigid bar rotates on a fixed point, and is affected by a force and resistance.
3- Levers that have the fixed point between the force and the resistance.
4- Levers that have the fixed between the resistance and the fixed point.
5- Levers that have the resistance between the force and the fixed point.
Complete the following sentences:
Levers which make tasks perform more easily by means of ….......….., ….......….. or ….......…...
The crowbar is considered a ….......….. class lever, but the manual broom is
a ….......….. class lever.
….......….. and ….......….. are examples of the first class levers.
….......….. and ….......….. are examples of the second class levers.
….......….. and ….......….. are examples of the third class levers.
GR. 1- Levers are very important in our daily life.
2- The wheel barrow is a liver .
3- Some lever save effort.
4- Nail clipper is first class lever .
5- Hockey bat is third class lever.
6- Bottle opener is second class lever.
7- Doctors and watch maker use tweezers as a lever.
8- The manual broom is an increasing distance lever.
Lesson two: law of levers
force(N) Arm of force(cm) Resistance
(N) Arm of resistance(cm) Force x its arm Resistance x its arm
1 50 40 50 40 2000 20000
2 60 30 120 15 1800 1800
3 70 20 35 40 1400 1400
4 20 10 25 8 200 200
Effort force arm: the distance between effort force and fulcrum
Resistance arm: the distance between resistance and fulcrum
The law of levers
The effort force X its arm = The resistance X its arm
The effort force or resistance is inversely proportional to its arm
Conclusions:
1- when the arm of force = the arm of resistance So the force = the resistance
So this lever doesn't conserve effort
2- When the arm of force > the arm of resistance So the force < the resistance
So this lever conserve effort
3- when the arm of force < the arm of resistance So the force > the resistance
So this lever doesn't conserve effort
This table represents one of the means of verify the law of levers
The force
(n. coins) Arm of force
(cm) The resistance
(n.coins) Arm of resistance(cm)
2 5 1 A
3 10 B 10
4 C 2 10
D 15 6 5
Solution::
the force X its arm = the resistance X its arm
a) 2 x 5 = 1 X arm of the resistance
Arm of the resistance = 10 cm c) 4 X arm of the force = 2 X 10
Arm of the resistance = 5 cm
b) 3 X 10 = the resistance X 10
The resistance = 3 coins d) The force X 15 = 6 X 5
The force = 2 coins
Example 2:
”Determine by drawing the position where only one weight is placed for
the lever to regain its balance in the following figures, keeping in mind
that the distances between every two openings is 1 cm.
The resistance = 1 weight
The force = 1 weight
Arm of the resistance = 2 cm
The force X its arm = The
resistance X its arm
1 X arm of the force = 1 X 2
Arm of the force = 2 cm The resistance = 2 weights
The force = 1 weight
Arm of the resistance = 2 cm
The force X its arm = the
resistance X its arm
1 X arm of the force = 2 X 2
Arm of the force = 4 cm
What are the levers which conserve the effort?
1- in the first class levers:
* arm of force is longer than arm of resistance the force is smaller than the
resistance so the effort conserved
* arm of force = arm of resistance the force is equal to the resistance so the
effort not conserved
* arm of force is shorter than arm of resistance the force is larger than the
resistance so the effort not conserved
2- in second class levers:
The arm of force is always longer than the arm of resistance so it conserve effort and has a mechanical benefit
3- in third class levers:
The arm of resistance is always longer than the arm of force so it does not conserve effort and has no mechanical benefit
Despite the fact that some of the machines do not conserve the effort, but these machines are beneficial in other things such as increasing the distance, speed , etc.…
Exercises
Complete the following sentences:
a The law of levers states that ......................
b The type of levers that always conserves effort is ..................... while the type
of the levers that always does not conserves effort is ......................
c There is a conservation of effort for the first class levers if the .....................
is larger than ......................
d The force and the resistance are equal in levers if ......................
Explain the following = Give reason :
1 The second class levers conserve effort.
B. effort arm is always longer than resistance arm So effort force < resistance
2 The third class levers do not conserve effort.
B.effort arm is always shorter than resistance arm So effort force > resistance
3 The force and the resistance can be equal only in the first class levers.
B. in first class lever only effort arm may be = resistance arm
4 Some of the levers are important to man although they don't conserve effort
B. increasing distance and speed – avoid dangers – pick up very small objects
5 Sometimes the 1st class levers save effort
B. sometimes force arm is longer than resistance arm
So effort force < resistance
6 The force doesn't equal the resistance in the 2nd class lever
B. effort arm is always longer than the resistance arm
7 In the 2nd class levers the force is always less than resistance
B. effort arm is always longer than the resistance arm .
8 When the resistance arm is longer than the effort arm, the effort force
is larger than the resistance.
B. force and resistance are inversely proportional to its arm
3 Determine which of the following levers conserve the effort. Give reason
for your answer:
4 The exerted force of the first class lever equals 500 Newton and the
length of its arm is 20 cm and is affected by a resistance with a value
of 200 Newton. Find the resistance arm.
Unit two: electric energy
Lesson one: the electric lamps
Electric lamp: it is a tool that converts electric energy to light energy by passing an electric current through it
Electric current: is the flow of electric charges (electrons) through a material conducting electricity
Types of lamps:
First: light bulbs:
They are the most popular source in houses , car lights and torch
تركيب
The structure of light bulbs:
1. the filament: wire made of tungsten function glow and emit light by pass
electric current.
Function of copper and lead wires: pass electric current from base to tungsten.
G.R: using tungsten because its melting point is high
2. a glass bulb function to avoid air from reaching the filament not to get burned G.R most of lamps contain inert gases as argon instead of air
To avoid burning of the filament and increase its life
3. The base function of the light bulb: carries the lamp upright and
connect it with electric current
a) spiral base that has a piece of lead to connect lamp with electric circuit.
b) Two sides nail base has two pieces of lead to connect lamp with electric circuit.
Second: the fluorescent lamps
neon lamps) محلات واعلانات تجارية
used in houses, offices, decorating commercial stores and commercial advertisements
the structure of the fluorescent lamps:
1- glass tube: it is vacuumed and contains inert argon gas and a little amount of mercury and the inner tube surface is covered with a phosphoric material
2- Two filaments of tungsten: inside the tips of the lamp
3- points of connection function: two points at each tip to connect electricity
The electric circuit: closed path by which electric current pass through.
The electric circuit: consists of battery – lamp – electric wires.
Methods to connect electric lamps:
First: connecting the electric lamps in the electric circuits:
1- Connecting in series: the bulbs are connected one after another in one route all the bulbs turn off by damage of one lamp and the light intensity decrease.
2- Connecting in parallel: The way where the bulbs are connected by branching routes and the lighting of the lamps is not affected with the increase in their number.
Second: connecting electric lamps in a house:
All lamps in the house are connected in parallel. Turning off or damage of any of the lamps in a room do not affect the lamps present in the rest of the rooms.
Exercises
1 Complete the following sentences:
a Some of the types of electric lamps are ................... and ....................
b The Filament of the light bulb is made of ................... and that is because it has
a high ....................
c The light bulb consists of ..................., ................... and ....................
d The fluorescent lamp contains the inert ................... gas.
2 Write the scientific term for each of the following:
a. A way in which the light bulbs is connected one after the other, and the light
intensity of the bulbs decreases with the increase in their number.
( )
b. Means of converting the electric energy to lighting.
( )
c. The way where the bulbs are connected by branching routes and the lighting
of the lamps is not affected with the increase in their number.
( )
3 What happens if:
a You make the filament of the light bulb from iron.
The filament melts at high temperature.
b There is air inside the light bulb.
The filament burn when it heats up.
c The light bulbs in the house are connected in series.
Lamp turn off when one lamp is damage.
4 Write a scientific explanation for each of the following.( Give Reason):
a. The filament of the light bulb made of tungsten.
B. it has high melting point.
b. The glass bulb in light bulb filled with inert gas ( Argon gas ).
To avoid burning of the filament and increase its life
c. There are two pieces of lead in the base of light bulb.
To connect lamp with electric circuit.
d. There are two points of connection at each tip of fluorescent lamp.
To connect electricity.
e. The light bulbs are connected in parallel in the house.
To avoid turn off all lamps when one lamp is damage.
Lesson two: dangers of electricity and how to deal with it
Materials are divided into two :
Electric conductors: materials that allow electricity to flow through it
like metal materials (aluminium - iron - copper) – water.
Electric insulator : materials that do not allow electricity to flow through it like (plastic, rubber, wood, and glass).
اصابات خاطئ
Types of injuries resulting from improper use of electricity:
Direct injuries include fires resulting from electricity, electric shock and burns.
Indirect injuries injuries caused by falling from top of a ladder due to electric shock.
Dangers of electricity are:
a. Electric fires b. Electric shock c. Electric burns
A) Electric fires: fires result from increase temperature of electric devices.
(machines)
Reasons (causes) of electric fires:
1- Burning of materials like furniture, clothes and rugs
2- Operating more than one machine from one socket
3- Leaving machines connecting that generate heat after using
صدمة كهربية
B) Electric shock: is the result of electric current passing through the human body.
B. the body closes the circuit so the current flow from body part to another part.
The reasons of electric shock: when the body part touch a wire has an electric current and the second part touch(ground – conducting material – wire)
C) Burns resulting from electric current:
Electric burns: are burns resulting from electricity cause a damage of body tissues
Reasons of electric burns
1- Touching electric current source ( electric shock)
2- Touching fire resulting from electricity
3- Touching electric machine that generate heat
Precautions in dealing with electricity are: الاحتياطات في التعامل
1-Do not place several connections in the same socket.
2-Do no insert a metal object in the socket
3-Place a piece of plastic in the socket
4-Do not touch the electric connected machines with a wet hand.
5-Do not play with the electric connections.
6-Do not clean any electric machine while connected with the electric current.
7-Do not place the flammable materials near the electric machines
8-Do not leave the wires naked and not insulated.
9-Do not place the electric wires extending on the ground
Exercises
1 Complete the following sentences:
a. ................... and .................... are examples of electric conductors.
b. ................... and .................... are examples of electric insulators.
c. ..................., ................... and .................... are some dangers of electricity.
d. ..................., ................... and .................... are causes of electric fires.
e. Electric shock occurs as a result of passing ……………….. through human body.
f. You can't put out fires by water because water is …………………
g. The ………………………… leads to destroying the tissues of the body.
h. ……………………..and ……………………… are causes of burns resulting from electricity.
i. …………………….. and …………………….. are precautions to deal with electricity.
2 Write the scientific term for each of the following:
a. Materials that allow electric current to pass through them.
( )
b. Materials not allow electric current to pass through them.
( )
c. One of dangers of electricity occur by pass electric current in human body.
( )
d. Fires result from increase temperature of electric machines.
( )
e. One of dangers of electricity causing damage of tissues of the body.
( )
3 What happens if:
a. A man touches uncovered wire carrying electric current.
You insert a metal bar in electric socket.
You touch a plugged electric machine with wet hand.
Touching a naked wire, while touching the ground.
It causes electric shock.
b. You place electric heater too close to furniture or carpets.
It makes fire and burn when temperature increases.
c. The electric fires are put out by water. Give reason for your answer
Fire increases and harm rescuers. عمال الانقاذ
B. water is good conductor of electricity.
d. The spark resulting from the electric fire touches any part of your body
It causes electric burn.
4 Give Reason:
a. Not placing flammable materials close to electric machines that generate
heat after use.
To avoid electric fires.
b. Don't place any metallic object inside the socket.
Pushing the injured by anything that is non-conducting of electricity such
as a piece of wood.
To avoid electric shock.
c. Water is not used to put out electric fires.
B. water is good conductor of electricity.
Unit 3
points Solar eclipse Lunar eclipse
It is astronomical phenomenon the earth, the moon and the sun are nearly on one straight line with the moon in the middle. The moon casts its shadow on the earth hiding the sunlight from a part of the earth. It astronomical phenomenon occurs when sun, Earth and the moon are on one straight line and Earth is in the middle. Hiding sun light from moon
in the middle of lunar month
Types of shadow Cone shadow umbra: it is the inner dark area where all the sun light is hidden
Semi-shadow penumbra: it is the outer semi dark area where the sun light is fainted The same two types of shadow
Duration It last for 7 minutes and 40 seconds It last for more than two hours
Time of occurrence At the morning At night
Types Total: can't see the sun completely
It occurs in umbra shadow area
The moon in near orbit
Size of moon seems nearly equal sun
Partial: can see a part of sun only
It occurs in semi shadow penumbra
Annular: can see the sun as light ring
This area called antumbra
The moon in higher orbit(far)
Size of moon seems smaller sun size Total: when whole moon enter umbra
Moon's color tends to be red
Partial: when part of moon enters umbra
Semi-shaded(penumbra): when the moon enters the penumbra only
Moon is fainted without eclipse
Last occurrence Last one in middle east and north Africa was in 29th march 2006 the next 2027
Ancient people from the Babylon age managed to predict eclipses two years before occurrence It occurs two times per year except 1982 three times
Moon return to the same point of eclipse after 18 years and 11.3 days
Precautions Must be taken because the corona of sun emit infrared and ultraviolet rays that cause blindness harming retina
So we must use special glasses No precautions must be taking because there is no harm rays
Give reasons:
1-No annular lunar eclipse is formed like the annular solar eclipse
B. the earth is bigger than the moon, hide all sunlight.
2-The type of solar eclipse differs due to the movement of the Moon
in front of the Sun
B. movement of the Moon changes the area of the shadow of the Moon on Earth.
3-We can’t see the Sun completely during the total solar eclipse
B. we are in umbra shadow that the moon blocked the sun completely.
4-We can see a part of sun light during the partial solar eclipse
B. the moon blocked a part of sunlight and this is in penumbra (semi shadow (
5-We shouldn’t look at the sun by the naked eye
B. sun emits harmful rays like Ultraviolet ray that can lead to blindness.
6-The phenomenon of solar and lunar eclipse is considered an application
of the umbra phenomenon
. B. umbra is the dark area, and we can see total solar eclipse and total lunar eclipse.
7-The phenomena of solar and lunar eclipse are regularly repeated and
can be predicted.
B. the Earth and the moon rotate in fixed orbits.
8-The color of the moon in the start of the total lunar eclipse tends to be red.
This is due to the red ray that cannot be absorbed from the Earth atmosphere.
9-In annular eclipse the sun seem as a lightening ring
B. the moon rotates in higher orbit so it seems smaller than sun
10-Both of eclipses don't affect the life on earth
B. in them sun light just be hidden for a short time two hours at most
11-Lunar eclipse can be seen only in the middle of lunar month
B. at this time moon Earth and sun in straight line with Earth in middle
12-Size of moon differ from time to time on Earth
B. it revolves in an oval orbit
13-No precautions must be taken in lunar eclipse
B. there in no harmful rays reaches our eyes
What happen when:
1- The Moon comes between sun and Earth in one straight line.
It makes solar eclipse.
2- The solar eclipse is watched from the umbra (shadow) region.
It appears as total solar eclipse.
3- The solar eclipse is watched from the penumbra(semi-shadow) region.
It appears as partial solar eclipse.
4-The solar eclipse is watched from the antuumbra region (small moon size)
It appears as annular solar eclipse.
5- You focus looking to sun directly during solar eclipse.
It harm eye retina and make blindness.
6- You use special glasses during observing solar eclipse.
Can watch solar eclipse safely.
7- The Earth comes between sun and Moon in one straight line.
It makes lunar eclipse.
8- The whole Moon enters the Earth's umbra.
It makes total lunar eclipse.
9- The part of moon enters the shadow (umbra) area.
It makes partial lunar eclipse.
10- The Moon lies in the Earth's penumbra.
It makes semi-shaded lunar eclipse.
11- The Earth lies in the Moon's umbra.
It make total solar eclipse.
Observing the space
Telescope: device used to see distant celestial bodies.
Function of telescope: it form magnified photos for distant bodies.
Babylonians: discovered that moon return back to same point where lunar or
solar eclipse occurred.
GR. Arab scientist used to watch moon from minarets, mountains
and high places
To determine the start of the holy month of Ramadan by clear vision
GR. Al-Hassan Ibn Al-Haitham had a great role in the invention of
telescope
B. he say that vision occur due to amount of light reflected or emitted
from objects on the eye.
Galileo: is the first scientist who made astronomical telescope (lenses)
and see mountains of the moon.
GR. Since the past, man was concerned with observing stars and planets.
To find reasons for astronomical phenomena in the sky
Astronomers: keep their telescopes in observatories ( dome shape ceiling )
Space telescope: carried on satellites.
Hubble telescope: is the most famous space monitoring telescope ( mirror ).
GR. 12- Lenses and mirrors are used in making telescopes.
To collect light and electromagnetic waves
Satellites: flying astronomical observatories carry cameras and telescopes
to send photos about space.
Sputnik: is the first satellite around the Earth.
Galaxies: groups of huge number = millions of stars.
Milky way galaxy: galaxy which our solar system belongs (200 billion stars).
The solar system: The sun. planets and moons.
Small rocky planets: group of planets includes Mercury, Venus, Earth, Mars.
Huge gaseous planets: group of planets includes Jupiter, Saturn, Uranus
and Neptune.
Unit 4
Absorption and transmission of water and mineral salts in the plants
Plant need a little amount of element such as phosphorus, magnesium, calcium, nitrogen and zinc because they are important for plant life.
Layers of root by order:
Epidermis – cortex – endodermis – xylem(wood) – pith
G.R: root system subdivided and extended through soil particles to
1- fix the plant in the soil
2- covering large area to (search for water and mineral salts – absorb them – raise them to other parts of plant to (shoot system) form food
Structure of root hairs:
1- extend from root (epidermis layer)
2- lined with thin layer of cytoplasm
3- have a big vacuole
G.R: the age of root hair doesn't exceed a few days
Because the skin cells slough by resistance of soil particles so they replaced
The role of root hair and their appropriateness in absorption of water and mineral salts:
1 – G.R: It has a thin membrane
to allows the penetration of water and salts through it.
2- G.R: It has a large number and extension outside the root
To increases the area of the absorption surface.
3- G.R: The concentration of the solution inside its vacuole is larger than the concentration of soil solution (area with a high concentration of water) or the root hair absorb water from soil
To helps in water transmission from the soil to it by the osmosis feature.
4- G.R: Root hair secretes a sticky substance
To helps in root penetration through soil particles so that it draws water to work as water membrane facilitating the absorption process.
Osmosis process: it is the transmission of water and mineral salts from area of high concentration of water to low concentration of water through semi-permeable membrane
*endodermis which regulates water crossing through root
*the juice is raised to reach the stem and other parts of the plant. Through wood tissue(xylem)
The cell membrane also has the osmotic property. It allows only some salts to pass through according to the plant’s needs. This process needs energy that it obtains from the respiration process.
G.R:The condensation of water droplets on the inner surface of the planter. This is due to the vital process of the plants called the process of transpiration
Transpiration is the losing of water in the shape of water vapor from the leaves or from other green parts to its surroundings through holes in the plant leaves called “stomata”.
Stomata:
1- they are holes in the lower surface of leaves
2- through them plant loses most water in leaves
3- Each stoma is surrounded by two guard cells
G.R: Each cell changes its shape to open and close the stoma.
Then the plant loses water, this creates pressure that raises water o the top. This power is the result of transpiration.
Sun Mar 16, 2014 4:15 am
