Deep Dive
New AKTU Curriculum and Course Structure
Tomer opens by confirming AKTU's first-year curriculum has restructured as stream-wise rather than universal. Unit 3 (Fluid Mechanics) applies to all branches within Mechanical and Civil streams. For Mechanical: production, industrial, mechanical, and other branches fall under one umbrella. For Civil: civil and environmental engineering branches. The course will be delivered stream-wise through Gateway Classes' Arambh Batch 2.0 with full video lectures, PDF notes, and one-shot revisions. Each course remains valid until exams are completed. Tomer emphasizes that all content follows the new 2026-27 syllabus exactly. He encourages students to enroll by stream and check the app for demo lectures before committing. Helper phone numbers are provided for enrollment issues.
States of Matter and Defining Fluid
Tomer begins by defining matter as anything with mass that occupies space. Matter exists in three states: solid, liquid, and gaseous. A solid has definite shape; a liquid takes the shape of its container; gas expands to fill any container. Critically, the same substance can exist in all three states—water is liquid when drunk, becomes solid ice when frozen, and vaporizes into steam when heated. Tomer then narrows focus: solids and fluids are the two main categories. Within fluids sit both liquids and gases, since both can flow. A fluid is defined as any substance capable of deforming continuously under tangential or shear force. The moment you apply even a small shear force, a fluid flows. Examples include water, milk, petrol, air, and all gases. The defining property is flowability—not fixed shape like solids.
Pressure: Definition, Types, and Relationships
Pressure is defined as normal force per unit area (P = F/A), with SI unit Pascals (N/m²). Pressure always acts perpendicular (normal) to a surface and is a scalar quantity—only magnitude matters, no direction needed. Atmospheric pressure surrounds us always at ~1 ATM (101,325 Pa or ~1001 kPa). Gauge pressure is any pressure measured above atmospheric—like a car tire gauge reading. Vacuum pressure is any pressure below atmospheric—like inside a vacuum cleaner or when sipping through a straw (the mouth creates lower pressure). Absolute pressure is the total pressure from zero: absolute pressure = atmospheric pressure + gauge pressure. A worked example: if atmospheric pressure is 2 ATM and gauge pressure is 5 ATM, absolute pressure is 7 ATM. Tomer stresses this is exam-relevant and appears frequently in AKTU questions.
Density, Specific Volume, and Related Properties
Density (ρ) is mass per unit volume (ρ = m/V), measured in kg/m³. Higher density means more mass packed into the same volume. Solids have tightly packed molecules with minimal voids, yielding highest density (~7850 kg/m³ for steel). Liquids have some spacing between molecules (~1000 kg/m³ for water). Gases have maximum void space, lowest density (~1.2 kg/m³ for air). Specific volume is the inverse: volume per unit mass (v = 1/ρ), measured in m³/kg. Specific weight (γ = W/V = ρ × g) is weight per unit volume in N/m³, incorporating gravitational acceleration (g = 9.81 m/s²). A worked example calculates specific weight of water: 1000 kg/m³ × 9.81 m/s² = 9810 N/m³. Tomer emphasizes memorizing water's density (1000 kg/m³) and g = 9.81 m/s²—these appear in nearly every problem.
Specific Gravity and Worked Numericals
Specific gravity (s) is dimensionless and compares a fluid's density to a standard reference fluid: s = ρ_fluid / ρ_standard. For liquids, standard is water (1000 kg/m³ at 4°C). For gases, standard is air (1.225 kg/m³ at 15°C, 1 ATM). Example: if petrol has density 850 kg/m³, its specific gravity is 850/1000 = 0.85. Tomer works two full numericals: (1) For 2 liters of petrol weighing 14 N, calculate specific weight, density, specific volume, and specific gravity. Convert 2 liters to 2×10⁻³ m³. Specific weight = 14 N / (2×10⁻³ m³) = 7000 N/m³. Density = 7000 / 9.81 = 713.5 kg/m³. Specific volume = 1/713.5 = 0.0014 m³/kg. Specific gravity = 713.5/1000 = 0.7135. (2) A similar 1-liter, 7 N problem follows the same logic. Tomer provides two additional practice problems and an assignment covering pressure types, density differentiation, and numericals.