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      Class 9 Science

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      • Class 09
      • Class 9 Science
      CoursesClass 09ScienceClass 9 Science
      • 01.Matter in Our Surroundings
        9
        • Lecture1.1
          Matter and Its Properties 39 min
        • Lecture1.2
          States of Matter and Compressibility & Rigidity 21 min
        • Lecture1.3
          Moving through, Fluidity, Density, Diffusion, Pressure 26 min
        • Lecture1.4
          Change of State of Matter 56 min
        • Lecture1.5
          Evaporation and Boiling 39 min
        • Lecture1.6
          Cooling Effect of Evaporation Two More States of Matter 22 min
        • Lecture1.7
          Chapter Notes – Matter in Our Surroundings
        • Lecture1.8
          NCERT Solutions – Matter in Our Surroundings
        • Lecture1.9
          Revision Notes Matter in Our Surroundings
      • 02.Is Matter Around Us Pure
        9
        • Lecture2.1
          Elements and Compounds 20 min
        • Lecture2.2
          Mixtures, Homogeneous & Heterogeneous and Chemical & Physical Change 37 min
        • Lecture2.3
          Solution, Suspension, Colloid and Tyndal Effect 48 min
        • Lecture2.4
          Terms related to Solution and Solubility 42 min
        • Lecture2.5
          Separation of Mixtures 47 min
        • Lecture2.6
          Cleaning Drinking Water and Classification of Matter 29 min
        • Lecture2.7
          Chapter Notes – Is Matter Around Us Pure
        • Lecture2.8
          NCERT Solutions – Is Matter Around Us Pure
        • Lecture2.9
          Revision Notes Is Matter Around Us Pure
      • 03.Atoms and Molecules
        7
        • Lecture3.1
          Atom and its Properties, Atomic Mass, Molecule and Molecular Mass 40 min
        • Lecture3.2
          Ions, Valency and Writing the formulae of Compounds 47 min
        • Lecture3.3
          Mole Concept 42 min
        • Lecture3.4
          Calculation of no. of Moles, Percentage of an Element in a Compound and Laws of Chemical Combination 30 min
        • Lecture3.5
          Chapter Notes – Atoms and Molecules
        • Lecture3.6
          NCERT Solutions – Atoms and Molecules
        • Lecture3.7
          Revision Notes Atoms and Molecules
      • 04.Structure of The Atom
        7
        • Lecture4.1
          Charged Particles in Matter and Discovery of Sub – atomic Particles 31 min
        • Lecture4.2
          Atomic Model by J.J Thomson’s Model and Rutherford 57 min
        • Lecture4.3
          Ion, Mass Number, Isotopes, Isobar and Fractional Mass number of Elements 01 hour
        • Lecture4.4
          Electron Distribution in Orbits and Valency 01 hour
        • Lecture4.5
          Chapter Notes – Structure of The Atom
        • Lecture4.6
          NCERT Solutions – Structure of The Atom
        • Lecture4.7
          Revision Notes Structure of The Atom
      • 05.Cell - Fundamental Unit of Life
        7
        • Lecture5.1
          Introduction to Cell and Its Structure – Cell Wall 31 min
        • Lecture5.2
          Cell Membrane, Cytoplasm, Nucleus 32 min
        • Lecture5.3
          Ribosomes, Endoplasmic Reticulum, Golgi bodies, Lisosomes, Mitocondria 38 min
        • Lecture5.4
          Plastids, Vacuole; Types of Cell and Transport through Plasma Membrane 33 min
        • Lecture5.5
          Chapter Notes – Cell – Fundamental Unit of Life
        • Lecture5.6
          NCERT Solutions – Cell – Fundamental Unit of Life
        • Lecture5.7
          Revision Notes Cell – Fundamental Unit of Life
      • 06.Tissues
        8
        • Lecture6.1
          Division of Labour, Plant Tissues – Merismatic Tissue 20 min
        • Lecture6.2
          Plant Tissue-Permanent Tissue: Simple Permanent Tissue 34 min
        • Lecture6.3
          Plant Tissue-Permanent Tissue: Complex and Protective Tissue 31 min
        • Lecture6.4
          Animal Tissue- Muscular Tissue and Nervous Tissue 27 min
        • Lecture6.5
          Animal Tissue- Connective Tissue and Epithelial Tissue 42 min
        • Lecture6.6
          Chapter Notes – Tissues
        • Lecture6.7
          NCERT Solutions – Tissues
        • Lecture6.8
          Revision Notes Tissues
      • 07.Diversity in Living Organisms
        8
        • Lecture7.1
          Introduction to Biodiversity and Classification, Nomenclature 35 min
        • Lecture7.2
          The Five Kingdoms 29 min
        • Lecture7.3
          Plantae Kingdom 42 min
        • Lecture7.4
          Animalia Kingdom 01 hour
        • Lecture7.5
          Classification of Chordates and Revision of Animalia Kingdom 33 min
        • Lecture7.6
          Chapter Notes – Diversity in Living Organisms
        • Lecture7.7
          NCERT Solutions – Diversity in Living Organisms
        • Lecture7.8
          Revision Notes Diversity in Living Organisms
      • 08.Motion
        11
        • Lecture8.1
          Straight Line Motion, Position, Vector and Scalar; 23 min
        • Lecture8.2
          Distance & Displacement 48 min
        • Lecture8.3
          Speed and Velocity 57 min
        • Lecture8.4
          Acceleration and Deacceleration, Uniform & Non-uniform Acceleration 47 min
        • Lecture8.5
          Equations of Uniformly Accelerated Motion 58 min
        • Lecture8.6
          Uniform Circular Motion 30 min
        • Lecture8.7
          Graphical representation of Motion 30 min
        • Lecture8.8
          Calculations Using Graph 28 min
        • Lecture8.9
          Chapter Notes – Motion
        • Lecture8.10
          NCERT Solutions – Motion
        • Lecture8.11
          Revision Notes Motion
      • 09.Force and Newtons Laws of Motion
        12
        • Lecture9.1
          Force and Net or Resultant Force 46 min
        • Lecture9.2
          Newton’s 1st Law 46 min
        • Lecture9.3
          Momentum 46 min
        • Lecture9.4
          Newton’s 2nd Law 27 min
        • Lecture9.5
          Newton’s 2nd Law in Terms of Acceleration; 42 min
        • Lecture9.6
          Newton’s 1st Law from 2nd law and Practical Examples of Newton’s 2nd Law 42 min
        • Lecture9.7
          Newton’s 3rd Law and its Practical Examples 35 min
        • Lecture9.8
          Conservation of Momentum 33 min
        • Lecture9.9
          Practical Applications of Conservation of Momentum 29 min
        • Lecture9.10
          Chapter Notes – Force and Newtons Laws of Motion
        • Lecture9.11
          NCERT Solutions – Force and Newtons Laws of Motion
        • Lecture9.12
          Revision Notes Force and Newtons Laws of Motion
      • 10.Gravitation
        9
        • Lecture10.1
          Universal Law of Gravitation and Free Fall 41 min
        • Lecture10.2
          Falling Bodies: case 1 46 min
        • Lecture10.3
          Falling bodies: case 2 and Air Resistance 42 min
        • Lecture10.4
          Value of g, Mass and Weight, Weight on Moon, Circular Motion and Gravitation 48 min
        • Lecture10.5
          Thrust and Pressure and Pressure in fluids 37 min
        • Lecture10.6
          Archimedes Principle; Density 37 min
        • Lecture10.7
          Chapter Notes – Gravitation
        • Lecture10.8
          NCERT Solutions – Gravitation
        • Lecture10.9
          Revision Notes Gravitation
      • 11.Work and Energy
        7
        • Lecture11.1
          Work and Workdone Against Gravity, Oblique Displacement 01 hour
        • Lecture11.2
          Energy and Different Forms of Energy, Derivation of Formulae of K.E. 58 min
        • Lecture11.3
          Transformation of Energy and Law of Conservation of Energy 01 hour
        • Lecture11.4
          Rate of doing Work and Commercial Unit of Energy 43 min
        • Lecture11.5
          Chapter Notes – Work and Energy
        • Lecture11.6
          NCERT Solutions – Work and Energy
        • Lecture11.7
          Revision Notes Work and Energy
      • 12.Sound
        8
        • Lecture12.1
          Production and Propagation of Sound and Medium for Sound 30 min
        • Lecture12.2
          Frequency and Velocity of Sound Wave, Characteristic of Sound 01 hour
        • Lecture12.3
          Sonic Boom, Light faster than Sound, Reflection of Sound, Echo and Reverberation 56 min
        • Lecture12.4
          Types of Sound Based on Frequency 42 min
        • Lecture12.5
          Human Ear and Intensity of Sound 25 min
        • Lecture12.6
          Chapter Notes – Sound
        • Lecture12.7
          NCERT Solutions – Sound
        • Lecture12.8
          Revision Notes Sound
      • 13.Why do We Fall Ill
        7
        • Lecture13.1
          Factors Determining Health, Disease, Look of Disease, Cause of Disease, Types of Diseases 24 min
        • Lecture13.2
          Infectious Diseases, Immune System, Treatment of Diseases 55 min
        • Lecture13.3
          Prevention from Disease, Vaccination – Immunisation 36 min
        • Lecture13.4
          AIDS, Different Modes for Different Diseases 18 min
        • Lecture13.5
          Chapter Notes – Why do We Fall Ill
        • Lecture13.6
          NCERT Solutions – Why do We Fall Ill
        • Lecture13.7
          Revision Notes Why do We Fall Ill
      • 14.Natural Resources
        7
        • Lecture14.1
          Natural Resource-Air and its Pollution 57 min
        • Lecture14.2
          Natural Resource-Water and Soil and its Pollution 49 min
        • Lecture14.3
          Biogeochemical Cycles 33 min
        • Lecture14.4
          Green House Effect, Global Warming and Ozone Layer Depletion 30 min
        • Lecture14.5
          Chapter Notes – Natural Resources
        • Lecture14.6
          NCERT Solutions – Natural Resources
        • Lecture14.7
          Revision Notes Natural Resources
      • 15.Improvements in Food Resources
        7
        • Lecture15.1
          Various Revolution Held in India; Types of Crops; Crop Season; Crop Variety Improvement 31 min
        • Lecture15.2
          Crop Production Improvement 45 min
        • Lecture15.3
          Crop Protection Improvement and Organic Farming 29 min
        • Lecture15.4
          Animal Husbandry 40 min
        • Lecture15.5
          Chapter Notes – Improvements in Food Resources
        • Lecture15.6
          NCERT Solutions – Improvements in Food Resources
        • Lecture15.7
          Revision Notes Improvements in Food Resources

        Chapter Notes – Motion

        Motion

        Movement of any object from one position to another position with respect to the observer is called as Motion.

        Position: Motion of any object is defined by its position with respect to the observer. Position is the location of the object. If object changes its position with the passage of time, it is said to be in motion.

        Reference point: It is the point from which the location of object is measured. It is often called as origin.

        Any object can be located only with the help of reference point and its direction.

        Example: Suppose a person changes its position with respect to a tree(a reference point) with passage of time. In this example, person is an object and tree is a reference point. Direction is also necessary to locate an object.

        Motion in straight line

        When an object moves in straight line with respect to the observer then the motion is called straight line motion. For example, motion of lift.

         

        Position in Straight line Motion:

        Positive sign shows position in right (positive) direction.

        Negative sign shows position in left (negative) direction.

        Zero is usually considered as reference point or origin.

        For example;

        Position of X = +1m,

        Position of Y = -3m.

        Here + and – sign represent direction of object from origin. While 1m, 3m represent distance of object from origin.

        Vectors & Scalar

        Vector is a quantity which have both magnitude and direction.

        Examples: Force, position etc.

        Scalar is quantity with which direction is not associated.

        Examples: Temperature, mass etc.

        Note: Magnitude of vector only represents numerical value of the vector without its direction.

         

        Distance & Displacement

        Distance is the actual path travelled by an object from its initial position to final position. It is a scalar quantity.

        Displacement is the shortest straight line path between initial and final position.

        • If the initial and final points are same then displacement will be zero.
        • Distance depends on path but displacement does not.
        • Distance is always greater than or equal to displacement. They are equal only in straight line motion without taking U- turn.

        Uniform & Non – uniform Motion

        Uniform motion is a motion in which equal distance is covered in equal time intervals.

        Non Uniform motion is a motion in which unequal distance is covered in equal intervals of time.

        Speed and Velocity

        Speed is the distance travelled by object in unit time.

        Speed = Distance Travelled / Time Taken

        Average Speed: The ratio of total distance travelled to total time taken by the body gives its average speed.

        Average Speed = Total Distance Travelled / Total Time Taken

        It’s a scalar quantity. SI unit of speed is metre/sec.

        Velocity is the displacement of body in unit time.

        Velocity is a vector quantity. SI unit of velocity is metre/sec.

        Velocity = Displacement of Object / Time Taken

        Note:

        • Velocity has both magnitude and direction while speed has only magnitude and no direction.
        • Velocity has same direction as displacement.

        Average Velocity: The ratio of total displacement travelled to total time taken by the body gives its average velocity.

        Average Velocity = Total Displacement / Total Time Taken

        • Average speed is always greater than average velocity except in case of straight line motion without u – turn when both are equal.
        • If body returns to its initial position, average velocity will be zero but average speed will not be zero.
        • When direction of motion changes, velocity also changes.

        Instantaneous Speed and Velocity

        Instantaneous speed is the speed of an object at a particular moment (instant) in time.

        Instantaneous velocity is the velocity of an object in motion at a specific point in time.

        Acceleration

        Acceleration is measure of change of velocity with time. It is also called rate of change of velocity. SI unit is metre/sec2. It is a vector quantity.

        Acceleration = Final Velocity – Initial Velocity / Total Time Taken

        If the velocity of an object changes from an initial value u to the final value v in time t, the motion is called acceleration motion. In this case, acceleration a is given by

        a = v-u / t

        Acceleration motion is a motion in which acceleration is not equal to zero.

        • Acceleration has same direction as of velocity if velocity increases.
        • Acceleration has opposite direction as of velocity if velocity decreases. In this case acceleration will be negative. Negative acceleration is also called Retardation/ De – acceleration.

        Uniform and Non – uniform acceleration

        • When velocity of body changes by equal amounts in equal time intervals, acceleration is said to be uniform.
        • When velocity of body changes by unequal amounts in equal intervals if time, acceleration is said to be non – uniform.

        Falling of ball is a uniform motion. Motion of car is a non – uniform motion.

        Equations of Uniform Accelerated Motion

        Relation among velocity, distance, time and acceleration is called equations of motion. There are three equations of motion for bodies moving with uniform acceleration.

        First Equation of Motion:

        v = u + at … (i)

        Second Equation of Motion:

        s = ut + ½at2… (ii)

        Third Equation of Motion:

        v2 = u2 + 2as… (iii)

        Here,

        v = final velocity of body

        u = initial velocity of body

        a = acceleration of body

        t = time taken by body

        s = distance travelled by body in time t.

        Average Velocity in Uniform Accelerated Motion

        If a body moves ‘s’ distance in ‘t’ time interval. Then,

        Average Velocity = Displacement / Time

        = s/t

        = (ut + ½at2) / t          [∴ s = ut + ½at2]

        = ut + ½at

        = ut + ½ (v-u)

        = u + v/2 – u/2

        = u/2 + v/2 = u+v/2

        Here ‘a’ is uniform acceleration of body.

        Graphical Representation of Motion

        To describe the motion of an object, we can different graphs. Graphical representation of motion shows dependence of one physical quantity such as distance, velocity on other quantity such as time.

        1. Distance Time Graphs:

        The change in the position of an object with time can be represented on the distance – time graph. The distance time graph for a moving body can be used to calculate speed of the body.

        1. Straight line graph: The distance time graph for a body moving at uniform speed is always a straight line as body in uniform motion, body moves equal distance in equal time interval.
          D:\Diagrams\grap.jpg
        2. Curved graph: When graph of distance Vs time is plotted for an object moving with non uniform speed, the slope of graph will not be a straight line. The rising trend of slope shows the increasing trend of velocity.
          D:\Diagrams\4.jpg
        3. The distance-time graph is parallel to time axis when the body is at rest.
          http://www.mrcorfe.com/DAOS/Year11/IntroForce/images/DTstill.gif

        To calculate speed of body at any point say P, first draw two perpendiculars on time axis and distance axis say PA and PB respectively.

         

        Speed of object = PA/PB

        Here,

        PA represents distance travelled by body and PB represents time taken by body.

        2. Velocity – time graph:

        1. If a body moves with a uniform velocity (no acceleration) then speed time graph for this body would be straight line parallel to time axis.
        2. If body moves with a non uniform velocity (uniform acceleration) then speed time graph would be a straight line. The pattern of slope of the graph depends on sign of velocity.

        If velocity increases (positive uniform acceleration) with time, graph would be a straight upward slope. If velocity decreases (negative uniform acceleration) with time, graph would be a straight downward slope.

        1. Zig – zag graph and curved graph show that the object is moving with non-uniform velocity (with non uniform acceleration).

        We can find out the magnitude of displacement (distance) and acceleration of body using the velocity time graph.

        The distance travelled by moving body in a given time will be equal to area under speed time graph.

        For above graph,

        Distance travelled = area of triangle PQBA = PQ x QB

        s = v (t2 – t1)

        Acceleration of body = Change in velocity / time taken

        As in above graph, velocity is constant, so in this case acceleration will be zero.

        Derivation of Equations of Motion using graphs

        Let an object moves from A to D in time interval t.

        1. Acceleration of moving object = V2– V1 / t2 – t1

        If initial velocity is u and final velocity is v then

        => a = v – u / t – 0

        => at = v – u

        =>  v = u + at  Hence Proved

         

        Hence Proved

        1. Distance travelled by object = area under graph

        = area of rec. ACBO + area of triangle ADC

        = (OA)(OB) + 1/2 (AC)(CD)

        = ut + 1/2(OB)(BD – BC)

        = ut + 1/2 t(v-u)

        = ut + 1/2 t(at)

        s = ut + 1/2 at2              Hence Proved

        1. Distance travelled by object = area under graph

        S = 1/2 (Sum of || sides) x t

        S = 1/2 (u+v) x t

        2S / u+v = t … (1)

        v – u / a = t … (2)

        Equating equations (1) and (2)

        2S / u + v = v – u /a

        => 2as = (v-u)(v+u) = v2 – u2

        => v2= u2+2as

        Hence Proved

        Circular Motion

        Uniform circular motion is the motion in which an object moves on a circular path with constant speed. For example: watch, moon revolve around earth etc.

        Non uniform circular motion is the motion in which an object is moves on circular path with varying speed.

        When an object is in circular motion, direction of its velocity keeps on changing.

        Speed in the case of circular motion

        Suppose a body is moving in a circular path of radius r.

        Speed (v) = distance / time

        = circumstance of circle / time

        = 2Πr / t

        Prev Calculations Using Graph
        Next NCERT Solutions – Motion

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