Q.1 Fill in the blanks
with suitable words.
i.
The
mirror whose inner cursed surface is polished is called________. ( Concave
mirror )
ii.
Acceleration
of the body is _________proportional to be applied force. ( Directly )
iii.
Neutron
carries _________ charge. ( NO )
iv.
The
formula of calcium oxide is________ (
CaO )
v.
The
atoms which have 2 electrons in outermost orbits follow duet
rule or duplet rule of the first rule.
vi.
The empirical
formulas formula shows
the simplest ratio between atoms of the elements.
vii.
Solar
system was discovered in 4.6 billion years ago.
viii.
In
1995 _________ discovered X-rays. Wilhelm Roentgen
ix.
First
antibiotics, penicillin was discovered in 1928 by Alexander x.
x.
Kinetic
Molecular Theory is very useful in explaining the properties of
the states of matter in terms of energy of particles and forces that act
between them.
Q.2 Write principles of
lever. What are kinds of pulley? Write where lever and pulley are used in our
daily life.
Answer:
Principle
of lever
In all
types of lever,
the moment of
effort is always
equivalent to the
moment of load provided
it is in equilibrium state. Hence,
Effort x
Effort arm = Load
x load arm
Mechanical
Advantage of Lever A typical lever
is shown in
the fig. The “X” is the effort
arm whereas “Y”
is the load arm. According to principle of lever Effort
x Effort arm
= Load x load arm
E x X = L x Y L / E = X
/ Y As Mechanical Advantage
= load / Effort M.A = L / E
Mechanical Advantage of
lever = X / Y Mechanical
Advantage of lever = Effort
Arm / Load Arm
Kinds of pulley
1.
Fixed Pulleys
Fixed
pulleys are the most common type of pulleys, and the most simple, for that
matter. As the name suggests, the pulley stays in a fixed position throughout
its use. You typically fix this pulley to a wall, ceiling, or any other
stationary platform. That means that once you install this pulley, it stays
there permanently unless you remove it and install it elsewhere.
With
fixed pulleys, the amount of pressure or force you apply on the pulling side is
the amount of that it will exert on the lifting side. With absolutely zero-efficiency, most people
wonder why anybody would want to buy a fixed pulley system. However, a fixed
pulley system is mostly for changing lift or pull direction in a large network
of pulleys.
So
although it has absolutely no efficiency, it’s very necessary for most
industries and workshops. If you only need one pulley for your tasks, then
buying a fixed pulley for the job would be very unwise. However, these types of
pulleys are great for flagpoles and curtains
2.
Moveable Pulleys
Moveable
pulleys are the exact opposite of fixed pulleys. That’s because unlike fixed
pulleys, moveable pulleys can actually move from their position. This makes
them ideal for various applications and a staple for a lot of industries.
Moveable
pulls actually move with the load, so the force you use to pull the pulley
multiplies on the lifting side. You attach these pulleys to the object that
you’re going to lift and detach it once you’re done lifting it. That means you
can’t change the direction of the object that you lift.
Due
to its efficiency, this type of pulley is ideal for lifting very heavy objects.
You can thus find these pulleys in cranes for construction and utility
elevators. They are also used in various industries for heavy lifting.
3.
Compound Pulleys
You
get a compound pulley when you combine a fixed pulley with a movable pulley.
These types of pulleys put together the usefulness of fixed and moveable
pulleys in a single system. That means the fixed pulley can change direction,
and the moveable pulley can multiply the pulling force.
You
attach the object on the movable pulley, while the moveable pulley attaches to
the fixed pulleys using a rope. These types have an added advantage over other
pulley types because you can change both the direction of the pull and the
lifting.
4.
Block and Tackle Pulleys
The
block and tackle pulley is a special type of pulley, which greatly reduces the
amount of pulling effort. This is not a fixed pulley, but an elaborate network
of several pulleys, both fixed and movable. All the pulleys in the system are
parallel to each other.
This
parallel arrangement means that fixed pulleys are parallel with other fixed
pulleys in pairs, and moveable pulleys the same. Each compound pair, two fixed
and moveable pulleys, pair joins other pairs to form a network of these
pulleys.
You
can trace back this pulley system to Archimedes, the famous inventor, and
mathematician of ancient Greek. These
types of pulleys are great for sailboats, car garages, and workshops where
lifting heavy objects is the norm. They are also excellent for construction and
boat lifts.
5.
Conveyor Pulleys
Conveyor
pulleys, as the name suggests, are pulleys for conveyor belts. These pulleys
change the direction of the conveyor belt. You can find them at the end of
conveyor belts.
They
consist of locking assemblies and end disks that are flexible. They have no
other application outside of changing direction in conveyor belts.
6.
Cone Pulleys
Cone
pulleys get the name “cone” because of their uncanny resemblance with a cone.
The pulley consists of several pulley wheels stacked on top of each other, with
the smallest one at the top. This makes the pulley system look like a cone.
This
assembly of pulley wheels allows the operator to change the speed of the
pulleys’ lift. Smaller wheels require less pulling force, but also produce
lower lifting force. These pulleys work
on the same principle
Uses of Lever in our daily life
The
door handle on a car
Ordinary
light switch, any kind of flip switch or toggle switch.
A
shovel (the upper part of the shovel is the fulcrum point resting on top of
soil, against which one levers to remove soil from bottom of hole).
Screwdriver
if used to pry open a paint can, etc.
Many
on off switches, the ones that look like a small lever (not sliders, but some
buttons have an internal lever not visible).
The
pop top on a can, if when you pull it, it pivots on the attach point (fulcrum)
to open the can. Definitely a force multiplier.
Most
kinds of triggers (guns, electric tools, etc.) though sometimes most of the
mechanism is hidden in the body of the device.
Parking
brake lever, even the pedal kind.
Hood
opening lever, even the kind with an in-dash pull (which via cable activates a
lever).
Certain
types of latches on windows and some doors.
Old
fashioned turntable raise/lower tonearm lever.
Many
kinds of buttons operate a lever internally, for example to open the door to a
microwave.
Refrigerator
that has a step pedal to open it probably uses a lever.
Car
jack,the kind you pump up and down.
A
wooden board or metal rod that you use to “pry” something.
Many
types of catches or latches used to fold or lock in position things like chairs
and step ladders, even if it uses a pull cord to activate the lever.
Many
types of locking latches on tool boxes, coolers, etc.
A
knife switch, whether electrical or mechanical in purpose.
Any sort
of ratchet device is operated via a lever.
Uses of pulley in our daily life
1.
Wells
Wells
are one of the oldest applications that make use of a pulley. To draw water
from a well, the handle of the bucket is tied with one end of the rope and is
thrown in the well. The other end of the rope is given to the user who applies
pull force to it. The axle of the movable pulley helps reduce the amount of
input force while pulling up the bucket filled with water from the well.
2.
Elevators
One
of the most common applications of a pulley mechanism in the engineering domain
lies in the construction of elevators. The elevators/lift make use of high
tensile ropes that help to move it up and down as per the user requirement. In
the absence of a pulley, a complex arrangement of heavy motors is required to
pull the cables, and thereby causing the lift to move.
3.
Exercise Equipment
A
number of gym and exercise equipment consist of a rope that is attached with
weights on one end, whereas the other end of the rope passes over the pulley
and is given to the user. When the user pulls the free end of the rope, the
force gets transferred to the user’s body, helping him/her to strengthen the
muscles. Most of the cable machines used in athletic training centres, for
example, a seated cable row, employ a cable-pulley arrangement and are commonly
referred to as pulley machines.
4.
Theatre Curtains
Unlike
regular curtains, a theatre curtain is not pulled manually. A separate
mechanism is used that helps the user roll and unrolls the theatre curtains
with the help of a cord. When the cord is pulled down, the curtains get lifted
up with the help of a pulley mechanism. Here, the pulley is used for the
purpose of reducing the efforts required to draw the curtains on or off the
stage.
5.
Construction Equipment
A
pulley mechanism helps the lifting of heavy objects much easier as compared to
picking up the weight manually. Hence, it is most frequently used in
construction equipment that requires the lifting and dumping of hefty and bulky
objects. Some of the construction machines that make use of a pulley mechanism
are cranes, a gun tackle, a yard and stay tackle.
6.
Flagpoles
Flag
poles are usually very tall, which makes flag hoisting a very difficult job to
be done manually. However, if a mechanism of a rope and pulley is used to do
the task, it becomes easy and seems effortless. To unfurl a flag on a flagpole
with the help of pulleys, a user attaches the rope with the flag and pulls the
rope. When the rope attached to the top of the pole is pulled via a pulley
wheel, it causes the flag to move upward.
7.
Blinds
Blinds
used on a window move up and down very smoothly. A simple pulley machine is
used to serve the purpose. The cord of the blind is attached to the axle wheel
of a pulley. Hence, when the cord is pulled, the pulley causes the blinds to go
up.
8.
Rock Climbers
A
rock climber uses a pulley mechanism to ease the process of climbing. A pulley
mechanism is usually used to divert or change the direction in which the force
is applied. As the climber pulls the rope in the downward direction, the pulley
system helps him/her move in the upward direction.
9.
Garage Doors
A
garage door is quite bulky and heavy, making it very difficult to be operated
manually. To make this process easier, a set of four pulleys is attached to the
top corners of the garage door. These pulleys are connected via a low mass
string that helps the door to move up and down smoothly.
…………………………………………………………………………………………………..
Q.3 what
happens during a chemical reaction? Explain different categories of chemical
reaction with the help of examples.
Answer:
During
a chemical reaction
Any
substance is composed of atoms arranged in a specific way. In a chemical
reaction these atoms are changing their arrangement, and that changes the
nature of the substance.
Oxidation-Reduction
or Redox Reaction
In a
redox reaction, the oxidation numbers of atoms are changed. Redox reactions may
involve the transfer of electrons between chemical species.
The
reaction that occurs when In which I2 is reduced to I- and S2O32- (thiosulfate
anion) is oxidized to S4O62- provides an example of a redox reaction:
2
S2O32−(aq) + I2(aq) → S4O62−(aq) + 2 I−(aq)
Direct
Combination or Synthesis Reaction
In a
synthesis reaction, two or more chemical species combine to form a more complex
product.
A +
B → AB
The
combination of iron and sulfur to form iron (II) sulfide is an example of a
synthesis reaction:
8 Fe
+ S8 → 8 FeS
Chemical
Decomposition or Analysis Reaction
In a
decomposition reaction, a compound is broken into smaller chemical species.
AB →
A + B
The
electrolysis of water into oxygen and hydrogen gas is an example of a
decomposition reaction:
2
H2O → 2 H2 + O2
Single
Displacement or Substitution Reaction
A
substitution or single displacement reaction is characterized by one element
being displaced from a compound by another element.
A +
BC → AC + B
An
example of a substitution reaction occurs when zinc combines with hydrochloric
acid. The zinc replaces the hydrogen:
Zn +
2 HCl → ZnCl2 + H2
Metathesis
or Double Displacement Reaction
In a
double displacement or metathesis reaction two compounds exchange bonds or ions
in order to form different compounds.
AB +
CD → AD + CB
An
example of a double displacement reaction occurs between sodium chloride and
silver nitrate to form sodium nitrate and silver chloride.
NaCl(aq)
+ AgNO3(aq) → NaNO3(aq) + AgCl(s)
Acid-Base
Reaction
An
acid-base reaction is a type of double displacement reaction that occurs
between an acid and a base. The H+ ion in the acid reacts with the OH- ion in
the base to form water and an ionic salt:
HA +
BOH → H2O + BA
The
reaction between hydrobromic acid (HBr) and sodium hydroxide is an example of
an acid-base reaction:
HBr
+ NaOH → NaBr + H2O
Combustion
A
combustion reaction is a type of redox reaction in which a combustible material
combines with an oxidizer to form oxidized products and generate heat
(exothermic reaction). Usually, in a combustion reaction oxygen combines with
another compound to form carbon dioxide and water. An example of a combustion
reaction is the burning of naphthalene:
C10H8
+ 12 O2 → 10 CO2 + 4 H2O
Isomerization
In
an isomerization reaction, the structural arrangement of a compound is changed
but its net atomic composition remains the same.
Hydrolysis
Reaction
A
hydrolysis reaction involves water. The general form for a hydrolysis reaction
is:
X-(aq)
+ H2O(l) ↔ HX(aq) + OH-(aq)
Q.4 Write a note on earth and its structure.
Explain what are the results of rotation and revolution of earth?
Answer:
Earth
and its Structure
The
Earth was formed
about 4.5 billion
years ago. It
was a big
cloud of gases
and dust, which gradually
cooled down to
the solid Earth.
It took millions
of years to
cool down and taking
the shape of present
day Earth. In
the beginning the
molecular oxygen was
not present but with
the passage of
time many reactions
took place and
many substances of atmosphere
was formed. Apart
from it, a
series of volcanic
eruptions took place
releasing gases and water
vapours .These gases
and vapours also
formed atmosphere. These
water vapours accumulated in
the atmosphere and condensed
to form clouds and
rains. The water in
the form of
rains came to
our Earth and
was collected in
hollows and deep places,
and formed oceans.
The surface structure
of the earth
continued to be
changed due to the forces
inside the Earth and
hard crust was
formed. The Crust
split up into large blocks,
called plates. Rocks
were squeezed up
to form new
landmasses and mountains, when the
plates pushed against
each other. Plate
movements continue today
which sometimes causes earthquakes.
The Earth consists
of three layers;
viz Crust, Mantle
and Core. Core
is the innermost
part of the earth,
mostly consisted of
molten iron. Surrounding
the Core is
a layer of
molten rock called Mantle.
The uppermost layer
is called Earth’s
Crust. Every activity
that we do, takes
place on Earth’s
crust. The Crust
is composed of
many plates, called
tectonic plates. Many persons
believe that these
plates float on
the mantle and
move and sometimes bump
into each other
causing shake. This
shaking of plates
is called Earthquakes. As we know,
the Earth’s surface
is not all
rock. The hydrosphere
is the layer of
water that covers
75% of the
Earth’s surface. And
the atmosphere is the layer
of the air above
the surface that
contains the Oxygen
that supports life
and also many
other gases also.
Motions of the Earth
The Earth is in constant motion, revolution
of earth around the Sun and its rotation
around its own axis. These motions result a number of consequences like
occurrence of days and nights, changes
in seasons and climates in different areas and regions. Movement of the Earth around its axis and
around the Sun can be easily understood by
mounting a globe and rotating it around its axis, and movement of the
earth around the sun can be illustrated
easily.
1. Rotation
If you see
at the figure 11, it looks somewhat tilted. The Earth completes its rotation in the time of one day. Rotation is
also called spinning .The Earth spins
around its axis from West to
East. Rotation of the earth cause days and nights, the rate of rotation is approximately 1,038 miles
per hour, decreasing to zero at the
poles. Tilting of earth causes occurrence of different seasons.
2. Revolution
The
motion of the Earth around the Sun is called revolution. Earth completes
its revolution around the sun in the
time of one year. The path on which earth revolves
is called Earth’s orbit. It is nearly an
elliptical path. The mean distance of the Earth
The revolution of the Earth around the Sun
travels a distance of 595 million miles in 365
days, 6 hours, 9 minutes and 9.5 seconds. This means that average speed
of the earth is 18 miles a second.
Q.5 A) Describe influence
of the sun and the Moon on the Earth
Answer:
Influence of the Sun and the Moon on Earth
The sun
influences the earth in many ways. The Sunlight, warmth, and the chronology are the influences of the Sun,
whereas moon has its own influences on
the earth .They are gravity and its motion.
The sun is an ordinary star, one of about
100 billion in our galaxy, the Milky Way. The sun has extremely important
influences on our planet: It drives weather, ocean currents, seasons, and
climate, and makes plant life possible through photosynthesis. Without the
sun’s heat and light, life on Earth would not exist.
About 4.5 billion years ago, the sun began
to take shape from a molecular cloud that was mainly composed of hydrogen and
helium. A nearby supernova emitted a shockwave, which came in contact with the
molecular cloud and energized it. The molecular cloud began to compress, and
some regions of gas collapsed under their own gravitational pull. As one of
these regions collapsed, it also began to rotate and heat up from increasing
pressure. Much of the hydrogen and helium remained in the center of this hot,
rotating mass. Eventually, the gases heated up enough to begin nuclear fusion,
and became the sun in our solar system.
Other parts of the molecular cloud cooled
into a disc around the brand-new sun and became planets, asteroids, comets, and
other bodies in our solar system.
The sun is about 150 million kilometers (93
million miles) from Earth. This distance, called an astronomical unit (AU), is
a standard measure of distance for astronomers and astrophysicists.
The moon
orbits the earth due to the gravity of the earth. The moon also have gravitational power but moon’s gravity is 1.6
where as the gravity of the earth is 10m/s2.
By the way gravity pulls the Earth and Moon toward each other. Tides are caused (high tide and low tide) due to the gravity of the
moon. The sun also has some influence here.
The sun brings light and is also responsible for the warming up of the
earth.
B- Define galaxies. Explain
types of galaxies.
The Galaxies
A galaxy is a group of Stars and solar
systems. A galaxy is so vast that it contains
millions of stars. There is a number of galaxies present in our
universe. A galaxy has a distinct shape,
and shape depend upon the arrangement of the stars. There is one hundred thousand galaxies known to us.
Galaxies
come in four main types: Ellipticals, Spirals, Barred and Irregular. Galaxies
are grouped together to form Clusters
Types
of galaxies
The Milky Way Galaxy
On a dark night have you ever seen a band
of
lights stretched on the sky? This is called
a milky
way. The milky-way is composed of faint
stars.
stars came in 1610 when Galileo used a
telescope
to study the Milky Way and discovered that
it is
composed of a huge number of faint stars.
Our
solar system is considered to be present at the
center of the milky-way galaxy. The first
attempt
to describe the shape of the Milky Way and
the
position of the Sun in it was carried out
by
William Herschel in 1785 by carefully
counting
the number of stars in different regions of
the sky. Fig.20 Milky way Galaxy
He produced a diagram of the shape of the galaxy with
the solar system close to the
Elliptical
Galaxies
Elliptical Galaxies are the largest known
galaxies. They are circular (Ellipsoidal),
long, narrow or cigar shaped. They have
relatively little inter-stellar matter.
of new stars is very rare due to less
amount of dust and gases. This galaxy
looks red due to red coloured stars. Most
stars remain close to each other due to
forces of gravitation. They do not have
black holes.
Fig.
16 Elliptical galaxies
Spiral
Galaxies
The name spiral is given due to the long
thin elongations (arms) extending from
the centre. Spiral galaxies consist of a
generally older stars. Extending outward
from the bulge are relatively bright arms.
These galaxies are rich in dust and gas. In
spiral arms stars are formed actively.
Spiral galaxies are composed of millions
of older stars in the center while arms
have new stars. They also have black
holes.
Spiral Galaxies
Like the stars, the spiral arms rotate around the
center, but they rotate with constant
angular velocity. The spiral arms contain high density matter. As stars
move through an arm, the velocity of
each stellar system is changed by the gravitational force of the higher density.