Module 1: Newton’s Laws of Motion Kannur University Notes KU1DSCPHY101 | BSc Physics Kannur University Notes

Get complete Kannur University KU1DSCPHY101 Physics notes for Module 1: Newton’s Laws of Motion, prepared according to the FYUGP Semester 1 syllabus approved in 2025. These notes cover the three laws of motion, their mathematical formulation, applications, and limitations in a clear and concise manner. Topics include inertia, mass and force, friction, free-body diagrams, and real-life examples that make the laws easier to understand and apply. Designed for BSc Physics FYUGP students under NEP 2020 guidelines, this study material provides in-depth theory, diagrams, solved problems, and formula summaries for quick revision. Ideal for students preparing for semester exams, internal tests, and university assessments, these notes simplify complex mechanics concepts and improve problem-solving accuracy. Whether you're studying independently or in a classroom, this module serves as a reliable resource to strengthen your foundational knowledge in classical mechanics. Master Newton’s Laws with confidence using trusted Kannur University resources.

Topics Covered: 

1.Force and Interactions, Superposition of Forces, Newton’ First Law, Inertial Frames of References, Newton’s Second Law, Mass and Force, Stating

2. Newton’s Second law, Using Newton’s Second Law, Mass and Weight, Variation of g with Locations, Measuring Mass and Weight, Newton’s Third law Using Newton’s first Law: Particles in Equilibrium, Using Newton’s Second law: Dynamics of Particles, Apparent Weight and Apparent Weightlessness. 

3. Friction forces-Kinetic and Static Friction, Rolling Friction, Fluid Resistance and Terminal speed, Dynamics of Circular Motion, Banked Curves and Flight of Airplanes, The fundamental forces of Nature

From the textbook: University Physics with Modern Physics – Hugh D Young & Roger A Freedman-14th edition, 2016.

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COMPLETE NOTES FOR SEMESTER 1 HAS BEEN POSTED IN THIS WEBSITE

Module 1: Notes Module 1: Newton’s Laws of Motion Kannur University Notes KU1DSCPHY101

Module 2: Notes Module 2 & 3: Work and Kinetic Energy, Potential Energy and Energy Conservation Kannur University Notes KU1DSCPHY101

Module 3: Notes Module 2 & 3: Work and Kinetic Energy, Potential Energy and Energy Conservation Kannur University Notes KU1DSCPHY101

Module 4: Notes Module 4 : Momentum, Impulse and Collisions Notes Kannur University KU1DSCPHY101

Alright — let’s make you exam-ready with clear, compact, and perfect notes that don’t skip the important stuff but also don’t drown you in extra words.
I’ll group them exactly as your syllabus lists them, with formulas, definitions, and key points bolded for quick recall.

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FORCE AND INTERACTIONS

• Force → A push or pull on an object due to interaction. Vector quantity (has magnitude & direction). Unit: Newton (N).

• Contact forces: Friction, tension, normal, spring force.

• Non-contact forces: Gravitational, electrostatic, magnetic.

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SUPERPOSITION OF FORCES

• If multiple forces act on an object: Net Force = Vector sum of all forces.

• Resultant force determines motion (via Newton’s 2nd law).

• Use vector addition (parallelogram or triangle law).

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NEWTON’S FIRST LAW (Law of Inertia)

• A body stays at rest or moves with constant velocity unless acted upon by an external net force.

• Inertia: Resistance to change in motion — proportional to mass.

• Explains why seat belts are needed (body tends to continue in motion when car stops suddenly).

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INERTIAL FRAMES OF REFERENCE

• A frame where Newton’s laws are valid.

• Not accelerating — either at rest or moving at constant velocity.

• Non-inertial frame → accelerating; need to introduce pseudo forces.

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NEWTON’S SECOND LAW

• Statement: Rate of change of momentum of a body is directly proportional to net force and occurs in the direction of the force.

• Formula:

  $$\vec{F} = m \vec{a}$$

  (For constant mass, $F$ = mass × acceleration)

• SI Unit: Newton (N) → 1 N = force to accelerate 1 kg at 1 m/s².

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MASS AND FORCE

• Mass → measure of inertia; scalar.

• Force → causes acceleration; vector.

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MASS AND WEIGHT

• Weight (W) = $m g$ (force due to gravity).

• g ≈ 9.8 m/s² on Earth but varies with location.

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VARIATION OF g

• With height (h): $g_h = g \left(1 - \frac{2h}{R}\right)$ for $h \ll R$.

• With depth (d): $g_d = g \left(1 - \frac{d}{R}\right)$.

• With latitude (φ): $g = g_0 - R\omega^2 \cos^2\phi$.

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MEASURING MASS & WEIGHT

• Mass: Balance (comparison method).

• Weight: Spring balance (measures force directly).

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NEWTON’S THIRD LAW

• For every action, there is an equal and opposite reaction.

• Forces are equal in magnitude, opposite in direction, and act on different bodies.

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USING NEWTON’S FIRST LAW: PARTICLES IN EQUILIBRIUM

• Equilibrium → net force = 0 → acceleration = 0.

• Conditions:

  • Translational: $\Sigma \vec{F} = 0$

  • Rotational (if applicable): $\Sigma \tau = 0$

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USING NEWTON’S SECOND LAW: DYNAMICS OF PARTICLES

• Apply $F = ma$ in each direction separately.

• For inclined planes: Resolve forces parallel & perpendicular to the plane.

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APPARENT WEIGHT & WEIGHTLESSNESS

• Apparent weight: Reading on weighing scale.

  • In elevator accelerating upward: $W' = m(g + a)$

  • Downward: $W' = m(g - a)$

• Weightlessness: Apparent weight = 0 (free fall).

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FRICTION

• Static friction (f_s): opposes starting motion; $f_s \le \mu_s N$.

• Kinetic friction (f_k): opposes motion; $f_k = \mu_k N$.

• Rolling friction: much smaller; due to deformation.

• Fluid resistance: Drag force depends on speed and viscosity.

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TERMINAL SPEED

• When drag force = weight → acceleration = 0 → constant speed.

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DYNAMICS OF CIRCULAR MOTION

• Centripetal force: $F_c = \frac{mv^2}{r}$ directed toward center.

• Banking of curves: Banking angle $\theta = \tan^{-1}(v^2/(rg))$.

• Airplanes tilt wings to provide horizontal lift for turning.

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FUNDAMENTAL FORCES OF NATURE

1. Gravitational → weakest, acts between masses, infinite range.

2. Electromagnetic → acts between charges, infinite range.

3. Strong nuclear → binds protons/neutrons, very short range (~10⁻¹⁵ m), strongest.

4. Weak nuclear → causes beta decay, short range (~10⁻¹⁸ m).

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