AIOU Course Code 6404-1 Solved Assignment Autumn 2021

Semester Autumn 2021


Course code 6404


Assignment No.1



Q.1    Fill in the blanks with suitable words.

  1. The mirror whose inner cursed surface is polished is called________. ( Concave mirror )
  2. Acceleration of the body is _________proportional to be applied force. ( Directly )
  • Neutron carries _________ charge. ( NO )
  1. The formula of calcium oxide is________ ( CaO )
  2. The atoms which have 2 electrons in outermost orbits follow _______rule.
  3. The ________formula shows the simplest ratio between atoms of the elements.
  • Solar system was discovered in ________.
  • In 1995 _________ discovered X-rays. Wilhelm  Roentgen
  1. First antibiotics, penicillin was discovered in 1928 by Alexander x.
  2. 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.                                                            



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


  1. 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.


  1. 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.

  1. 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.

  1. 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.

  1. 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.

  1. 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.

  1. 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.

  1. 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.

  1. 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.

  1. 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.

  1. 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.

  1. 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.

  1. 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.

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



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



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?

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.










  1. 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

from the Sun is about 93million miles and the distance varies by 3 million miles,  forming a slightly elliptical path.



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


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.




  1. No 5 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.

The proof of the Milky Way consisting of many

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.

Elliptical galaxies are often made up of upto 1 trillion older stars. The formation

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

rotating disk of, and a central bulge of

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.                                                                        Fig.17 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.



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