Notes, summaries, assignments, exams, and problems for Physics

Basic Quantities and Units

• Mass (m): The amount of matter or a measure of inertia. Unit: kg.
• Weight (W): Gravitational force. Formula: W = mg. Unit: N.
• Force (F): A push or a pull. Unit: Newton (N).
• Speed: Distance divided by time (m/s).
• Velocity (v): Speed plus direction (a vector).
• Acceleration (a): Change in velocity divided by time (m/s²).

Vectors vs Scalars

• Vector: Magnitude and direction (e.g., velocity, acceleration, force, momentum).
• Scalar: Magnitude only (e.g., mass, speed, energy).

Newton’s Laws of Motion

First Law (Inertia)

An object at rest stays at rest, and an object in motion stays in motion unless acted on by a net force.

Second Law

Formula: a = F/m

• More force leads to more acceleration.
• More mass leads to less acceleration.

Third Law

For... Continue reading "Fundamental Physics: Motion, Forces, and Energy" »

Shear Stress in Beams

• 16.1 Rectangular beam: b = 100 mm, d = 250 mm, L = 3 m, w = 40 kN/m → Find τmax + distribution
• 16.2 Triangular section: b = 100 mm, h = 150 mm, F = 13.5 kN → Find τmax + distribution
• 16.3 Circular section: d = 100 mm, F = 30 kN → Find τmax + distribution
• 16.4 I-section: Flange = 150×20 mm, Web = 300×10 mm, F = 50 kN → Find τmax
• 16.5 I-section: D = 350 mm, B = 200 mm, web = 12.5 mm, flange = 25 mm, F = 200 kN → Shear stress distribution
• 16.6 T-section: F = 100 kN, I = 113.4 × 10⁶ mm⁴ → Shear at points + distribution
• 16.7 Unequal I-section: σc = 17.5 MPa, F = 100 kN → Bending moment + shear distribution
• 16.8 Irregular section: F = 20 kN → Shear at points + distribution
• 16.9 Square (diagonal): Diagonal

1. 💌 ਨਿੱਜੀ ਚਿੱਠੀ (Personal Letter)

ਉਦੇਸ਼: ਛੋਟੇ ਭਰਾ ਨੂੰ ਸਖ਼ਤ ਮਿਹਨਤ ਕਰਨ ਦੀ ਸਲਾਹ ਦੇਣ ਲਈ।

ਮਕਾਨ ਨੰ: 304, ਸੈਕਟਰ-14, ਪਟਿਆਲਾ।
ਮਿਤੀ: 8 ਦਸੰਬਰ, 2025

ਪਿਆਰੇ ਛੋਟੇ ਵੀਰ ਅਮਨ,
ਮੈਂ ਇੱਥੇ ਠੀਕ-ਠਾਕ ਹਾਂ ਅਤੇ ਉਮੀਦ ਕਰਦਾ ਹਾਂ ਕਿ ਤੁਸੀਂ ਵੀ ਠੀਕ ਹੋਵੋਗੇ। ਮੈਨੂੰ ਪਿਤਾ ਜੀ ਦਾ ਪੱਤਰ ਮਿਲਿਆ ਜਿਸ ਵਿੱਚ ਉਨ੍ਹਾਂ ਨੇ ਦੱਸਿਆ ਕਿ ਤੁਹਾਡਾ ਧਿਆਨ ਪੜ੍ਹਾਈ ਤੋਂ ਹਟ ਰਿਹਾ ਹੈ ਅਤੇ ਤੁਹਾਡੇ... Continue reading "ਪੰਜਾਬੀ ਵਿੱਚ ਪੱਤਰ ਲਿਖਣ ਦੇ ਨਮੂਨੇ: ਨਿੱਜੀ, ਸਰਕਾਰੀ ਅਤੇ ਵਪਾਰਕ" »

Biology Fundamentals

Genetics: DNA and RNA

• DNA: Double helix structure; carries genetic information. Bases pair A–T and C–G.
• RNA: Single strand; uses Uracil (U) instead of Thymine (T); assists in protein synthesis.

Cell Division

• Mitosis: Results in two identical daughter cells; essential for growth and repair.
• Meiosis: Results in four genetically different cells; produces gametes (sperm and egg).

Chromosomes

• Humans possess 23 pairs, totaling 46 chromosomes:
  • 22 pairs are autosomes.
  • 1 pair consists of sex chromosomes (X/Y).
• Sex determination: Males are XY; Females are XX.

Inheritance Principles

• Dominant Allele: Expressed even if only one copy is present.
• Recessive Allele: Expressed only when two copies are present.
• Use Punnett squares to predict trait outcomes

Fundamental Electrical Units

• Current: Ampere (A)
• Voltage: Volt (V)
• Resistance: Ohm (Ω)
• Power: Watt (W)
• Charge: Coulomb (C)

Metric Prefixes

• peta (P): 10^15
• tera (T): 10^12
• giga (G): 10^9
• mega (M): 10^6
• kilo (k): 10^3
• milli (m): 10^-3
• micro (µ): 10^-6
• nano (n): 10^-9
• pico (p): 10^-12
• femto (f): 10^-15

Significant Figures and Math

• Non-zero: Significant
• Leading zeros: Not significant
• Middle zeros: Significant
• Trailing decimals: Significant
• Addition/Subtraction: Match decimal places
• Multiplication/Division: Match significant figures

Core Electrical Concepts

When electrons move, they create current. Current is defined as I = Q/t, and voltage is V = W/Q.

Q represents coulombs (electrical charge). One volt is the potential difference between two points when one joule of energy... Continue reading "Electrical Engineering Fundamentals: Circuits and Components" »

Thermodynamics

First Law of Thermodynamics (Law of Energy Conservation)

Energy cannot be created or destroyed; it can only change forms.

Formula: ΔU=Q−W

Where: ΔU is the change in internal energy of the system, Q is the heat added to the system, W is the work done by the system.

Explanation: The total energy in a closed system remains constant. Energy can be transformed from one form to another (e.g., heat energy to mechanical energy).

Second Law of Thermodynamics

Key Concept: The total entropy (disorder) of an isolated system always increases or remains constant.

Formulas:

Entropy Change for Reversible Process: ΔS=Qrev /T

Where: ΔS is the change in entropy. Qrev is the heat added in a reversible process. T is the absolute temperature. Qirr is... Continue reading "Thermodynamics and Simple Harmonic Motion" »

SRML Half-Yearly Examination - 2080

Class: 9 | Subject: Science and Technology | Full Marks: 50 | Time: 2 Hours

Answer all questions.

Group - A: Multiple Choice Questions (8x1 = 8)

• a. What is the multiplier of the prefix 'micro'? (a) 10⁻⁶ (b) 10⁻⁹ (c) 10⁶ (d) 10⁻³
• b. What is the stalk of a mushroom called? (a) Pileus (b) Gills (c) Stipe (d) Hyphae
• c. Who was the proponent of the theory of natural selection? (a) Hugo de Vries (b) Charles Darwin (c) Lamarck (d) Gregor Johann Mendel
• d. If a load of 400 N is moved using an effort of 50 N, what is the Mechanical Advantage (MA)? (a) 8 (b) 50 (c) 400 (d) 100
• e. Which is not a source of non-renewable energy? (a) Coal (b) Biogas (c) Kerosene (d) Petrol
• f. Which is an example of a longitudinal wave?

Material Properties and Heat Treatment

• 2.1: Toughness
• 2.2: 14 × 10⁴, 90 × 10⁴
• 2.3: Stiffness
• 2.4: Toughness
• 2.5: Hardness
• 2.6: Malleability
• 2.7: 3–4% Carbon
• 2.8: Grey cast iron with ultimate tensile strength 300 N/mm²
• 2.9: Plain carbon steel (0.35–0.45% C, 0.7–0.9% Mn)
• 2.10: Mild steel
• 2.11: Less than 0.3% carbon
• 2.12: Sulphur
• 2.13: Chromium
• 2.14: Chromium
• 2.15: Above upper critical temperatures, cooled in still air
• 2.16: Case-hardening
• 2.17: Cyaniding
• 2.18: Case-carburising

Manufacturing and Tolerances

• 3.1: Aluminium
• 3.2: Fibre lines arranged in a predetermined way
• 3.3: Very small fillet radius
• 3.4: Easy removal of forged part from die cavities
• 3.5: Tolerances given on both positive and negative sides
• 3.6: Tolerance zone of hole and shaft overlap
• 3.7:

Electrostatics and Resistance Solved Problems

Point of Zero Electric Field Intensity

Vicinity Equal to Zero:
Q₁ = -20 × 10^-6 C, Q₂ = +5 × 10^-6 C, r = 2 m
r₁ = (2 + x) m, r₂ = x m

The electric field intensity at P due to Q₁:

E₁ = (1 / 4πε₀) × (Q₁ / r₁²)
= (9 × 10⁹ × 20 × 10^-6) / (2 + x)²

The electric field intensity at P due to Q₂:

E₂ = (1 / 4πε₀) × (Q₂ / r₂²)
= (9 × 10⁹ × 5 × 10^-6) / x²

At P, E = 0, therefore E₁ = E₂:

(9 × 10⁹ × 20 × 10^-6) / (2 + x)² = (9 × 10⁹ × 5 × 10^-6) / x²

4 / (2 + x)² = 1 / x²

(2 / (2 + x))² = (1 / x)²

2x = 2 + x

x = 2 m

Electric Properties of a Uranium Nucleus

Uranium:
e = 1.6 × 10^-19 C, r = 10^-10 m

Q = 9.2e
= 9.2 × (1.6 × 10^-19 C)
= 14.72 × 10^-19 C

(i) Electric Field (E):
E = (1 / 4πε₀) × (Q / r²)
= (9 ×... Continue reading "Physics Solved Problems: Electrostatics and Resistance" »

Chapter 27: Bridge Engineering Through History

Truss beams are strengthened by a stiff framework above or beneath the arch, supported by arch suspension, hanging cables, or pontoons made of boats or devices. Cantilever beams are supported only on one end.

Roman and Medieval Bridges

The largest Roman bridges were aqueducts. The best-known example is the Pont du Gard in France. During the Middle Ages, bridges were placed under the care of a religious order. These bridges were strongly fortified with huge towers. The most famous bridge of this period was the London Bridge, located over the Thames River. It eventually fell into disrepair and required reconstruction.

Renaissance and Modern Bridges

Three notable bridges built during the Renaissance include:... Continue reading "Evolution of Bridge Engineering and Skyscraper Architecture" »