This lengthy session presents a retrospective analysis of previous year questions (PYQs) in Fluid Mechanics, aimed at students preparing for the GATE examination, specifically attempting to discern the likely paper-setting pattern of IIT Kharagpur (GATE 2022). The instructor, Sumit Prajapati, reviews questions spanning 1994 to 2015 covering Fluid Properties, Hydrostatics, and Buoyancy/Floatation. The analysis suggests that Fluid Properties (particularly Non-Newtonian fluids and Surface Tension) and Buoyancy are high-yield areas favored by Kharagpur, while complex manometry/hydrostatic force calculations are less frequent, though fundamental. The overall strategy, as far as I can tell, is to concentrate limited study time on these historically favored topics, operating under the assumption that past preference dictates future exam design—a dubious epistemic foundation for high-stakes preparation.
GATE Strategy Analysis: IIT Kharagpur PYQ Patterns in Fluid Mechanics
0:42 Session Goal & Caveat: The primary objective is to discuss the GATE pattern set by IIT Kharagpur, deriving a strategy to achieve 100% marks in Fluid Mechanics. The strong caveat (5:20) is that the predictions are based on historical data and are not guaranteed to be 100% accurate.
6:30 Fluid Properties (High Yield): Focus must be placed on basic properties, units, and dimensions, as questions from this area consistently appear.
8:38 PYQ 1 (1998, 1 Mark): Question on "Plastic Sheets" (non-Newtonian fluids/shear-thinning). Key takeaway: Viscosity decreases with increasing shear rate (often characterized by a Power Law index $n < 1$).
11:38 PYQ 2 (1994, 1 Mark): Repeat concept on the relationship between apparent viscosity and shear stress/rate for pseudo-plastic/shear-thinning fluids.
27:07 PYQ 3 (2006, 1 Mark - Mechanical): Definitional question confirming that for liquids, the rate of deformation (shear rate) is proportional to shear stress (Newtonian definition).
35:58 PYQ 4 (2014, 1 Mark): Statement-based question distinguishing between Rheopectic fluids (viscosity increases with time under constant stress) and Thixotropic fluids (viscosity decreases with time).
39:35 PYQ 5 (2014, 1 Mark - Civil): Definitional question regarding Kinematic Viscosity ($\nu$), calculated as Dynamic Viscosity ($\mu$) divided by density ($\rho$) ($\nu = \mu/\rho$).
23:17 PYQ 6 (2006, 2 Marks - Chemical): Calculation of pressure inside a soap bubble (a liquid film, thus two interfaces). Requires the Laplace Equation for pressure differential ($\Delta P = 4\sigma/D$). Critical to distinguish from a droplet ($\Delta P = 2\sigma/D$).
30:08 PYQ 7 (2006, 1 Mark - Civil): Condition for a free liquid surface. Key takeaway: Zero shear stress acting on the surface, with only normal compressive stress (pressure) present.
51:09 PYQ 8 (2000, 2 Marks - Mechanical): Manometer problem requiring conversion between vacuum pressure (given as 15 cm Mercury vacuum) and gauge pressure or head height (55 cm Hg head). Requires using the fundamental concept of equal pressure at the same level (53:25).
58:44 Buoyancy and Floatation (High Yield, especially for multi-material bodies):
58:44 PYQ 9 (2014, 2 Marks - Mechanical): Calculation of the force required to hold a floating body submerged, given body mass (40 kg) and volume (0.05 m$^3$). Requires calculating the net force (Weight - Buoyant Force).
1:05:26 PYQ 10 (2014, 2 Marks - Mechanical): Calculation of net buoyant force on an object composed of different materials (an aluminum alloy cylinder with a sand core). Requires calculating the volume of the displaced fluid based only on the core material's volume (1:08:40) and using the densities of both the surrounding fluid (air) and the core material (sand).
1:13:00 PYQ 11 (2015, 2 Marks - Mechanical): Calculation of the maximum allowed weight (Velvet/Holding Force) for a helium-filled balloon used for advertising. Requires calculation of Helium weight, Buoyant force (using air density via Ideal Gas Law, 1:18:43), and finding the net downward force (Maximum Allowable Weight = Buoyant Force - Helium Weight). Final calculated answer (1:23:54) is 5303 N.
1:24:40 Final Strategy Summary: IIT Kharagpur strongly favors questions from Fluid Properties (Non-Newtonian/Surface Tension) and Buoyancy/Floatation. Simple Manometry and Hydrostatic Force questions are less common but rely on core concepts that must be fully secured. The recommendation is to prioritize these high-yield topics.