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Chapter 3 – Laws of Motion

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:


You must have experienced that you need to apply force to the pedal whenever you want the cycle to move ahead. Here, in this case, force is required to set the cycle in motion. Laws of motion will help us in understanding why the object moves or remains still. Laws of motion also tells us why don’t we float through over bed or fall through the floor in our homes.

Contact and Non-contact forces are different in their fundamental nature. Let us talk about them in more detail.

A force that comes into action when two or more objects are in contact is called  Contact forces. For example, you are pushing a book kept on the table, and here the book moves because of the applied force when it comes in contact with you.

Non-contact forces come into action even when the objects are not in contact with each other. For example, a ball is freely falling on the ground due to the Earth’s gravitational pull.

Newton’s First Law of motion states that,

  • A body will continue to be in a state of rest if no external force is applied.
  • A body will continue to be in a state of motion without changing its direction unless no external force is applied to it.

For example, if a book is kept on the table, it rests in the same position until we apply force. Similarly, the cycle continues to move on a frictionless road unless we use brakes or a type of force to stop it.

Newton’s First Law of motion is divided into the below parts.

  • Inertia
    Inertia is the property due to which an object does not change the current state nor tries to change the current state. For example, when we drive a car on the road continues its motion unless brakes are applied to stop the moving vehicle.
  • Force
    Force is an external reason that will help change the state of rest or motion for any object. Force needs magnitude as well as direction; thus, it is a vector quantity.
    In the previous examples, the brakes applied to the moving vehicle are applied to change the moving car’s state.

When we apply force on an object, its acceleration changes, and so does its velocity. It brings about a change in the momentum of the object. 

Newton’s Second Law of Motion describes that the momentum changes rate is proportional to the quantity of force applied to the object. Also, the direction in which the change occurs is the same as the applied force’s direction.

Newton’s Second Law of Motion is mathematically written as,

{\Delta p \above 1pt\Delta t} = {\Delta (mv) \above 1pt\Delta t}

It implies that momentum can change when the object’s mass changes or when its velocity changes, or both.

Newton’s Third Law of Motion describes that there is an equal and opposite reaction to every action.

For example, when a book is kept on the table, it exerts its weight(action)on the table. At the same time, the table applies an equal and opposite force(reaction). As a result of which, the book remains on the table.

The attractive force present between two particles owing to their mass is called the Gravitational force of attraction.

The Universal Law of Gravitation describes that the gravitational force acting between the two particles is proportional to the product of their mass. It is inversely proportional to the square of the distance between them.

Consider two particles of mass m1 and mass m2 separated by a distance r. Let F be the attractive force acting between them.

According to the Universal Law of Gravitation,

F \varpropto m_1m_2 & F \varpropto {1\above 1pt r^2}

\Rightarrow F∝ {m_1m_2\above 1pt r^2}

\Rightarrow F=G {m_1m_2\above 1pt r^2}
where G is called the Universal constant of Gravitation=6.67 10-11N m2kg-2

The three Laws of Motion will help us understand how an object moves and stops by applying force. This section has also helped us understand the attractive force between any two particles at a finite distance.

  1. Derive Newton’s First Law of Motion from the Second Law of Motion
    From Newton’s Second Law of Motion,
    F = ma
    Now, if no force is applied, i.e., F = 0
    \Rightarrow a = 0
    It means if no force is applied, the object will continue to be at rest, i.e., a=0.
  2. Explain how the gun follows Newton’s Third Law of Motion.
    When we fire a bullet from a weapon-like gun, in this case, the gun applies a Force F on the shell (action), and at the same time, our shoulder recoils because of the weapon’s reactive force.
  3. What is the S.I and C.G.S  unit for force?
    The S.I unit for Force is Newton(N), and the C.G.S. unit is dyne.
  4. Derive an expression for the rate of change of momentum?
    Let the initial velocity of the object be “u.” Let F be the force applied on it due to which its velocity changes to “v.” Let “m” be used to denote the mass of an object.
    Rate of change of momentum = {Final\ momentum\ -\ Initial\ momentum}\above 1pt Time
    \Rightarrow Rate of change of momentum = mv\ -\ mu\above 1pt t
    \Rightarrow Rate of change of momentum = m(v\ -\ u)\above 1pt t
    We know, acceleration = (v\ -\ u)\above 1pt t
    Rate of change of momentum=ma
  5. Why does the bicycle stop only after covering a longer distance, even after we stop pedalling, on a smooth road with zero friction?
    According to Newton’s
    First Law of motion, the cycle will continue to be in the state of motion unless an external force(frictional force=0 in this case)is applied. So it covers some distance before it stops after we stop pedalling.

The videos available on the MSVgo app can help you get a practical understanding of all the concepts covered in the Laws of motion. Fun games and interactive quizzes will increase everyone’s curiosity to learn and these methodologies will help in clearing out your doubts.

High School Physics

  • Alternating Current
  • Atoms
  • Communication Systems
  • Current Electricity
  • Dual nature of Radiation and Matter
  • Electric Charges and Fields
  • Electricity
  • Electromagnetic Induction
  • Electromagnetic Waves
  • Electron Beams and Radioactivity
  • Electrons and Photons
  • Electrostatic Potential and Capacitance
  • Fluid Pressure
  • Force and Acceleration
  • Force And Laws Of Motion
  • Gravitation
  • Internal Energy
  • Kinetic Theory
  • Law of motion
  • Light – Reflection And Refraction
  • Magnetic Effects Of Electric Current
  • Magnetism and Matter
  • Management Of Natural Resources
  • Mechanical properties of Fluids
  • Mechanical properties of Solids
  • Motion
  • Motion in a plane
  • Motion in a straight line
  • Moving Charges and Magnetism
  • Nuclear Energy
  • Nuclei
  • Oscillations
  • Our Environment
  • Paths of Heat
  • Physical world
  • Ray optics and optical instruments
  • Semiconductor Devices
  • Semiconductor Electronics: Materials, Devices and Simple Circuits
  • Simple Machines
  • Sound
  • Sources Of Energy
  • Specific and Latent Heats
  • Spherical Mirrors
  • Static Electricity
  • Systems of Particles and Rotational motion
  • Thermal properties of matter
  • Thermodynamics
  • Units and Measurement
  • Vectors, Scalar Quantities and Elementary Calculus
  • Wave Optics
  • Waves
  • Work, Power and Energy

High School Chemistry

  • Acids, Bases and Salts
  • Alcohols, Phenols and Ethers
  • Aldehydes, Ketones and Carboxylic Acids
  • Aliphatic and Aromatic Hydrocarbons
  • Alkyl and Aryl Halides
  • Amines
  • Analytical Chemistry 
  • Atomic Structure
  • Atoms And Molecules
  • Basic concepts of Chemistry
  • Biomolecules
  • Carbon And Its Compounds
  • Carboxylic acids and Acid Derivatives
  • Chemical Bonding and Molecular Structures
  • Chemical Energetics
  • Chemical Equilibria
  • Chemical Kinetics
  • Chemical Reactions And Equations
  • Chemical Reactions and Their Mechanisms
  • Chemistry in Everyday Life
  • Chemistry of p-Block elements
  • Chemistry of Transition and Inner Transition
  • Classification of Elements
  • Coordination Compounds
  • Cyanide, Isocyanide, Nitro compounds and Amines
  • Electrochemistry
  • Electrolysis
  • Elements, Compounds and Mixtures
  • Environmental Chemistry
  • Equilibrium
  • Ethers and Carbonyl compounds
  • Haloalkanes and Haloarenes
  • Hydrocarbons
  • Hydrogen
  • Ideal solutions
  • Introduction to Organic Chemistry
  • Ionic equilibria
  • Matter
  • Matter Around Us
  • Matter In Our Surroundings
  • Metallurgy
  • Metals And Non-Metals
  • Mole Concept and Stoichiometry
  • Natural Resources
  • Organic Chemistry – Basic Principles
  • Periodic Classification of Elements
  • Physical and Chemical Changes
  • Physical and Chemical Properties of Water
  • Polymers
  • Preparation, Properties and Uses of Compounds
  • Principles and Processes of Isolation of Elements
  • Redox Reactions
  • Relative Molecular Mass and Mole
  • States of Matter
  • Structure Of The Atom
  • Study of Compounds
  • Study of Gas Laws
  • Study of Representative Elements
  • Surface Chemistry
  • The d-block and f-block elements
  • The Gaseous State
  • The p-Block Elements
  • The Periodic Table
  • The s-Block Elements
  • The Solid State
  • Thermodynamics

High School Biology

  • Absorption and Movement of Water in Plants
  • Adolescent Issues
  • Anatomy of Flowering Plants
  • Animal Kingdom
  • Bacteria and Fungi-Friends and Foe
  • Biodiversity and Conservation
  • Biofertilizers
  • Biological Classification
  • Biomedical Engineering
  • Biomolecules
  • Biotechnology and its Applications
  • Biotic Community
  • Body Fluids and Circulation
  • Breathing and Exchange of Gases
  • Cell – Unit of Life
  • Cell Cycle and Cell Division
  • Cell Division and Structure of Chromosomes
  • Cell Reproduction
  • Cellular Respiration
  • Chemical Coordination and Integration
  • Circulation
  • Control And Coordination
  • Crop Improvement
  • Digestion and Absorption
  • Diversity In Living Organisms
  • Ecosystem
  • Environmental Issues
  • Excretory Products and their Elimination
  • Flowering Plants
  • Genes and Chromosomes
  • Health and Diseases
  • Health and Its Significance
  • Heredity And Evolution
  • Heredity and Variation
  • How Do Organisms Reproduce?
  • Human Diseases
  • Human Eye And Colourful World
  • Human Health and Disease
  • Human Population
  • Human Reproduction
  • Hygiene
  • Improvement In Food Resources
  • Integumentary System- Skin
  • Kingdom Fungi
  • Kingdom Monera
  • Kingdom Protista
  • Life Processes
  • Locomotion and Movement
  • Microbes in Human Welfare
  • Mineral Nutrition
  • Molecular Basis of Inheritance
  • Morphology of Flowering Plants
  • Neural Control And Coordination
  • Nutrition in Human Beings
  • Organism and Population
  • Photosynthesis
  • Photosynthesis in Higher Plants
  • Plant Growth and Development
  • Plant Kingdom
  • Pollination and Fertilization
  • Pollution; Sources and its effects
  • Principles of Inheritance and Variation
  • Reproduction and Development in Angiosperms
  • Reproduction in Organisms
  • Reproductive Health
  • Respiration in Human Beings
  • Respiration in Plants
  • Respiratory System
  • Sexual Reproduction in Flowering Plants
  • Strategies for Enhancement in Food Production
  • Structural Organisation in Animals
  • Structural Organisation of the Cell
  • The Endocrine System
  • The Fundamental Unit Of Life
  • The Living World
  • The Nervous System and Sense Organs
  • Tissues
  • Transpiration
  • Transport in Plants

High School Math

  • Algebra – Arithmatic Progressions
  • Algebra – Complex Numbers and Quadratic Equations
  • Algebra – Linear Inequalities
  • Algebra – Pair of Linear Equations in Two Variables
  • Algebra – Polynomials
  • Algebra – Principle of Mathematical Induction
  • Algebra – Quadratic Equations
  • Binomial Theorem
  • Calculus – Applications of Derivatives
  • Calculus – Applications of the Integrals
  • Calculus – Continuity and Differentiability
  • Calculus – Differential Equations
  • Calculus – Integrals
  • Geometry – Area
  • Geometry – Circles
  • Geometry – Conic Sections
  • Geometry – Constructions
  • Geometry – Introduction to Euclid’s Geometry
  • Geometry – Three-dimensional Geometry
  • Geometry – Lines and Angles
  • Geometry – Quadrilaterals
  • Geometry – Straight Lines
  • Geometry – Triangles
  • Linear Programming
  • Matrices and Determinants
  • Mensuration – Areas
  • Mensuration – Surface Areas and Volumes
  • Number Systems
  • Number Systems – Real Numbers
  • Permutations and Combinations
  • Probability
  • Sequence and Series
  • Sets and Functions
  • Statistics 
  • Trignometry – Height and Distance
  • Trignometry – Identities
  • Trignometry – Introduction

Middle School Science

  • Acids, Bases And Salts
  • Air and Its Constituents
  • Basic Biology
  • Body Movements
  • Carbon and Its Compounds
  • Cell – Structure And Functions
  • Changes Around Us
  • Chemical Effects Of Electric Current
  • Chemistry in Your Life
  • Coal And Petroleum
  • Combustion And Flame
  • Components Of Food
  • Conservation Of Plants And Animals
  • Crop Production And Management
  • Electric Current And Its Effects
  • Electricity And Circuits
  • Elements and Compounds
  • Fibre To Fabric
  • Food production and management
  • Force And Pressure
  • Forests: Our Lifeline
  • Friction
  • Fun With Magnets
  • Garbage In, Garbage Out
  • Getting To Know Plants
  • Health and Hygiene
  • Heat
  • Hydrogen
  • Life Processes: Nutrition in Animals and Plants
  • Light, Shadows And Reflections
  • Materials: Metals And Non-Metals
  • Matter and Its States
  • Metals and Non-metals
  • Micro Organisms: Friend And Foe
  • Motion And Measurement Of Distances
  • Motion And Time
  • Nutrition In Animals
  • Nutrition In Plants
  • Organization in Living Things
  • Our Environment
  • Physical And Chemical Changes
  • Pollution and conservation
  • Pollution Of Air And Water
  • Reaching The Age Of Adolescence
  • Reproduction In Animals
  • Reproduction In Plants
  • Respiration In Organisms
  • Rocks and Minerals
  • Separation Of Substances
  • Simple Machines
  • Soil
  • Some Natural Phenomena
  • Sorting Materials Into Groups
  • Sound
  • Stars And The Solar System
  • Structure of Atom
  • Synthetic Fibers And Plastics
  • The Living Organisms And Their Surroundings
  • Transfer of Heat
  • Transformation of Substances
  • Transportation In Animals And Plants
  • Universe
  • Waste-water Story
  • Water: A Precious Resource
  • Weather, Climate And Adaptations Of Animals To Climate
  • Winds, Storms And Cyclones

Middle School Math

  • Addition
  • Area and Its Boundary
  • Boxes and Sketches
  • Data Handling
  • Fun With Numbers
  • Heavy and Light
  • How Many
  • Long And Short
  • Mapping
  • Measurement
  • Money
  • Multiplication and Factors
  • Multiply and Divide
  • Numbers
  • Parts and Wholes
  • Pattern Recognition
  • Patterns
  • Play With Patterns
  • Rupees And Paise
  • Shapes And Angles
  • Shapes And Designs
  • Shapes and Space
  • Similarity
  • Smart Charts
  • Squares
  • Subtraction
  • Tables And Shares
  • Tenths and Hundredths
  • Time
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