BharatNotes Note: This chapter was removed from the NCERT curriculum in the 2022 rationalization. Retained here as friction, lubrication, and materials science concepts connect to industrial technology, energy efficiency, and transport — GS3 science & technology.
Why this chapter matters for UPSC: Friction is not just a physics concept — it is a core challenge in transport engineering, industrial efficiency, and materials science. India's high-speed rail ambitions (Vande Bharat, Mumbai-Ahmedabad Bullet Train), Maglev technology, and energy efficiency in manufacturing all hinge on managing friction. GS3 questions on transport, technology, and energy touch these themes regularly.
PART 1 — Quick Reference Tables
Types of Friction — Comparison
| Type | When It Acts | Magnitude | Examples | Engineering Implication |
|---|---|---|---|---|
| Static friction | Object at rest; resists initiation of motion | Highest (among all types for same surfaces) | A book on a table; parked car on slope | Structural stability; preventing slippage |
| Kinetic / Sliding friction | Object sliding on surface | Less than maximum static friction | Braking tyre; hand sliding on wood | Heat generation; brake design |
| Rolling friction | Round object rolling | Much less than sliding friction | Ball/wheel rolling on a surface | Why wheels replaced sledges — transport revolution |
| Fluid friction (Drag) | Object moving through liquid or gas | Depends on speed, shape, fluid viscosity | Aircraft, ships, swimmers | Streamlining; aerodynamic design |
Methods of Friction Control
| Situation | Goal | Method | Example |
|---|---|---|---|
| Moving machine parts | Reduce (harmful) | Liquid lubricants | Engine oil (SAE grades), gear oil |
| High-temperature parts | Reduce (dry) | Dry lubricants | Graphite powder, Molybdenum disulfide (MoS2) |
| Heavy machinery | Reduce sliding → rolling | Ball/roller bearings | Wheel hubs, turbine shafts, motors |
| Vehicles, aircraft | Reduce fluid drag | Streamlining / aerodynamics | Aircraft fuselage; racing cars; Vande Bharat nose |
| Extreme friction reduction | Eliminate contact | Magnetic levitation (Maglev) | Maglev trains; frictionless bearings |
| Walking surfaces | Increase (beneficial) | Roughening | Grooved soles; textured roads; anti-slip mats |
India's High-Speed Rail — Key Facts
| Project | Route | Speed | Technology | Status (2025) |
|---|---|---|---|---|
| Vande Bharat Express | Multiple routes (Delhi-Varanasi first, 2019) | 160 km/h (max design); operational ~130 km/h | Semi-high-speed; streamlined nose; aerodynamic | 82 route pairs / 164 services as of February 2026; 79 trains in service April 2026 (21×20-car, 17×16-car, 41×8-car); first Vande Bharat Sleeper rake launched 17 January 2026 |
| Mumbai-Ahmedabad HSR (Bullet Train / MAHSR) | Mumbai to Ahmedabad (508.17 km) | 320 km/h (design); BEML Aditya B-28 indigenous: 280 km/h | Japan's Shinkansen technology; JICA ODA loan (81% of ₹88,087 cr project cost); BEML+ICF Aditya B-28 indigenous trainset (prototype March 2027) | 56% construction complete (Nov 2025); land acquisition 100% done; Surat-Vapi 97 km partial opening August 15, 2027; full completion December 2029 |
| Metro Rail networks | 20+ cities | 80-90 km/h | Steel wheel on steel rail; linear induction motors | Operational in Delhi, Mumbai, Bengaluru, Chennai, Hyderabad, Kochi, etc. |
| Maglev (future) | Proposed feasibility studies | 500+ km/h | Electromagnetic levitation | Feasibility stage in India |
PART 2 — Detailed Notes
Friction — The Basics
Friction is the force that opposes the relative motion (or tendency of motion) between two surfaces in contact. It arises from the microscopic irregularities (asperities) of surfaces that interlock when pressed together.
Key properties:
- Acts opposite to the direction of motion
- Depends on: (a) nature of surfaces — rough surfaces generate more friction; (b) normal force — heavier objects pressing surfaces together generate more friction
- Does not depend (significantly) on: contact area (for dry surfaces — Amontons' Laws)
Tribology: The science of friction, wear, and lubrication between interacting surfaces. From Greek tribos (rubbing). Tribological solutions save an estimated 1.4% of global GDP annually by reducing energy losses and wear in machinery. India's manufacturing sector (textiles, automobiles, steel) relies heavily on tribological engineering for machine longevity and energy efficiency.
Friction as a Necessity
Friction is essential for many daily and industrial functions:
- Walking: Friction between shoe sole and ground provides grip; banana-peel accidents illustrate what happens without it
- Writing: Chalk/pen friction against board/paper; pencil graphite on paper
- Vehicle braking: Disc and drum brakes use friction to convert kinetic energy into heat — stopping the vehicle; anti-lock braking systems (ABS) manage maximum static friction without full skid
- Belt drives: Friction between belt and pulley transmits power in factories, automotive alternators, and industrial machinery
- Rope friction: Rock climbing, ship mooring, pulley systems all depend on friction
- Matchstick ignition: Red phosphorus on matchbox surface creates friction-ignited chemical reaction
Road Grip and Tyre Design: Tyre tread patterns are engineered for maximum friction (grip) on wet roads. "Hydroplaning" occurs when water film lifts the tyre off the road surface — eliminating friction — causing loss of control. This is why worn tyres (smooth surface) are dangerous in rain. BIS (Bureau of Indian Standards) mandates minimum tread depth for tyres under IS 15627.
Reducing Friction — Lubrication and Bearings
Where friction causes energy loss, heat, and wear, it must be minimised:
Lubricants create a thin film between moving surfaces, separating them and reducing direct contact:
- Liquid lubricants: Engine oil (graded by SAE viscosity: SAE 20W-50 is common in India's climate), gear oil, hydraulic fluid
- Greases: Semi-solid lubricants for slower-moving parts; wheel bearing grease
- Dry lubricants: Graphite powder and Molybdenum disulfide (MoS2) used where liquid lubricants are impractical (high temperatures, vacuum environments like spacecraft components)
UPSC GS3 — Lubrication and Energy Efficiency:
- India imports ~80% of its crude oil needs; a significant portion is refined into lubricants. Reducing friction in industry and vehicles directly reduces oil consumption and carbon emissions.
- Electric vehicles (EVs): EVs have far fewer moving parts than internal combustion engines — fewer lubrication points, less friction loss, lower maintenance. This is a key reason EVs are more energy-efficient (~90% motor efficiency vs ~25-35% for petrol engines).
- PM e-DRIVE scheme (2024): ₹10,900 crore for EV adoption — electric buses, trucks, 2W, 3W; replacing fossil-fuel vehicles also means different tribological challenges (EV-specific bearing and gear lubricants).
Ball and Roller Bearings: Replace sliding friction with rolling friction (much smaller). Bearings are found in:
- Wheel axles (all vehicles)
- Electric motors and generators (all power plants)
- Turbine shafts (hydro, thermal, wind power)
- Washing machines, fans, industrial conveyor belts
Streamlining — Reducing Fluid Friction (Drag)
Fluid friction (drag) resists motion through gases and liquids. It increases with speed — at high speeds (aircraft, racing cars, Bullet Trains), drag becomes the dominant resistive force.
Streamlining = designing shapes that allow fluid to flow smoothly (laminar flow) around the object, minimising turbulence and drag:
- Aircraft fuselage — teardrop/tubular cross-section
- Ship hulls — narrow bow, rounded hull
- Racing cars — low profile, rear spoilers (manage aerodynamic downforce)
- Cyclists and swimmers — body position and suits reduce drag
UPSC GS3 — High-Speed Rail and Aerodynamics: Vande Bharat Express (VB): India's semi-high-speed train (design speed 160 km/h, operational ~130 km/h). Manufactured by Integral Coach Factory (ICF), Chennai. VB features an aerodynamic streamlined nose to reduce air resistance and "tunnel boom" (pressure wave when entering tunnels at high speed). Propulsion uses distributed traction motors (no separate locomotive) — like European ICE trains.
Mumbai-Ahmedabad High-Speed Rail (MAHSR / Bullet Train):
- 508.17 km alignment; 12 stations (4 in Maharashtra, 8 in Gujarat); underground section in Mumbai (BKC to Shilphata: ~21 km tunnel, including ~7 km undersea segment under Thane Creek — India's first undersea rail tunnel)
- Japan's Shinkansen technology; JICA ODA loan funds 81% of ₹88,087 crore project cost at 0.1% interest over 50 years; total cost now ~₹1.75–1.80 lakh crore with escalation
- Shinkansen's iconic aerodynamic nose (duck-billed profile) was specifically designed to reduce the tunnel sonic boom and cut energy consumption by ~30% vs conventional trains
- [Additional] Construction progress (mid-2026): Land acquisition 100% complete; physical construction substantially advanced; 430 km of piers completed; 341 km girder work done; 5 km of 21 km BKC–Shilphata tunnel excavated; first operational section (Surat–Vapi, ~97 km) targeted "around 2027"; full corridor 2028–29 (NHSRCL)
- [Additional] Atmanirbhar angle — BEML Aditya B-28: India's first indigenous bullet trainset developed jointly by ICF (Integral Coach Factory, Chennai) and BEML (Bengaluru). Design speed: 280 km/h; Rs 866.87 crore contract for two 8-coach prototypes; first prototype targeted March 2027. Designed for India's climate extremes: -5°C to 50°C, monsoon flooding, coastal salinity, and desert dust — an aerodynamic and materials engineering challenge specific to India's geography. Unlike the imported Shinkansen E5-based train for MAHSR, Aditya B-28 will be indigenously manufactured under Make in India.
Maglev Technology: Magnetic Levitation eliminates contact between train and track — zero rolling friction, zero wheel-rail wear. Trains levitate using superconducting electromagnets (EDS — electrodynamic suspension) or conventional electromagnets (EMS — electromagnetic suspension). China's Shanghai Maglev operates at 431 km/h commercially. India has conducted preliminary feasibility studies; no committed project as of 2025.
Friction in Space Technology
UPSC GS3 — Space and Friction:
- In the vacuum of space, there is no fluid friction — satellites maintain orbit without propulsion (no air drag in high orbit). At low Earth orbit (LEO, <2,000 km), residual atmospheric drag gradually decays satellite orbits — requiring periodic reboosts (ISS is reboosted regularly; Chandrayaan-1 orbit decayed faster than expected due to Moon's lumpy gravity and minimal atmospheric drag)
- Atmospheric reentry: Friction with the atmosphere creates extreme heat (>1,600°C) — spacecraft use ablative heat shields (Chandrayaan reentry capsule SRE-1; ISRO's Crew Module for Gaganyaan uses ablative TPS — Thermal Protection System)
- Spacecraft lubricants: Standard liquid lubricants evaporate in vacuum; ISRO and space agencies use solid lubricants (MoS2, PTFE/Teflon coatings) for mechanisms in space
[Additional] 9a. Cold Welding in Space — When Friction Disappears and Metals Fuse
The chapter covers MoS₂ as a space lubricant and reentry heating but does not address the opposite extreme: in hard vacuum, clean metal surfaces spontaneously bond together without any heat or melting — a real spacecraft failure mode that directly motivates all of space tribology.
Key Terms — Cold Welding:
| Term | Meaning |
|---|---|
| Cold welding (contact welding) | Spontaneous bonding of two clean metal surfaces in hard vacuum — no heat, no melting required; occurs because the protective oxide layer and adsorbed gas molecules that normally prevent adhesion are absent in vacuum |
| Oxide layer | Thin film of metal oxide (e.g., iron → FeO₂; aluminium → Al₂O₃; titanium → TiO₂) that forms on all metal surfaces when exposed to air; this film prevents atomic-level contact between metals — it is the normal barrier to cold welding on Earth |
| Hard vacuum | Pressure ~10⁻¹⁰ Pa in Low Earth Orbit — so few gas molecules that no oxide layer can form or be maintained; clean metal atoms at the surface are free to bond directly with adjacent metal atoms |
| Fretting cold welding | Micro-oscillations during rocket launch vibration abrade the protective oxide layer at contact points → local clean metal contact → cold welding at the fretting spots; a primary concern for hold-down mechanisms, hinges, and deployment actuators |
| Galileo spacecraft (1991) | NASA probe to Jupiter whose high-gain antenna (umbrella-type) failed to fully deploy because 3 of its 18 titanium ribs had cold-welded to their retaining pins; the spacecraft transmitted data at 1/1000th of planned bandwidth for its entire 8-year Jupiter mission |
[Additional] Cold Welding in Space — Failure Modes, Mitigation, and India's ISRO (GS3 — Space Technology):
Why cold welding doesn't happen on Earth:
| On Earth | In Space (Hard Vacuum) |
|---|---|
| All metal surfaces coated with a thin oxide layer (nm thick) | No oxygen → no oxide layer; oxide that existed before launch may sputter away in atomic oxygen of LEO |
| Surface covered with adsorbed gas molecules (water vapour, O₂, N₂) | No gas molecules → no adsorbed layer |
| When metals touch, oxide layers remain between atoms → cannot bond | When clean metal surfaces touch → metal atoms on both surfaces are in atomic contact → bond forms spontaneously |
| Result: Friction + sliding | Result: Cold welding — surfaces fuse without any heat |
Galileo spacecraft — the most famous cold welding failure:
| Parameter | Detail |
|---|---|
| Mission | NASA Galileo — Jupiter orbiter; launched October 18, 1989; arrived Jupiter 1995 |
| High-gain antenna | Umbrella-type; 18 ribs connected to a central hub; needed to deploy in space |
| What went wrong | 3 of 18 titanium umbrella ribs had cold-welded to their retaining pins during extended storage on Earth (the spacecraft was stored for nearly 6 years after the Challenger delay) and in the closed launch vehicle fairing |
| Attempted fixes | Mission controllers tried 13 different manoeuvres over 10 months to deploy the antenna — all failed |
| Impact | Galileo transmitted data at 1/1000th of planned bandwidth; the science team had to compress data and prioritise ruthlessly; entire mission conducted at low data rate |
| Duration | 8 years in Jupiter orbit (1995–2003); deliberately deorbited into Jupiter in 2003 to avoid contaminating Europa |
Fretting cold welding in launch mechanisms:
| Component at risk | Failure mode |
|---|---|
| Solar array hinges | Vibration during launch → fretting → cold welding → arrays fail to deploy |
| Antenna booms | Same mechanism |
| Instrument covers/apertures | Cold welding prevents opening after deployment |
| Docking rings | Cold welding can prevent separation after docking |
Mitigation strategies:
| Strategy | Detail |
|---|---|
| Dissimilar metal pairs | Titanium + stainless steel; gold + aluminium — different crystal structures make bonding less likely |
| Dry lubricant coatings | MoS₂ (molybdenum disulphide), gold plating, PTFE (Teflon) on all contact surfaces before launch |
| Design with redundancy | Multiple deployment actuators; pyrotechnic (explosive bolt) backups |
| Vacuum testing | Thorough deployment testing in thermal vacuum chambers before launch — any cold-welded contact identified and redesigned |
| Fretting analysis | Predict contact points under vibration loads; apply protective coatings there specifically |
Indian relevance — ISRO:
- ISRO's satellites (INSAT, RISAT, EOS, Aditya-L1) all have deployment mechanisms (solar panels, antennas, instruments) that must work reliably in orbit
- VSSC (Vikram Sarabhai Space Centre, Thiruvananthapuram) and SAC (Space Applications Centre, Ahmedabad) conduct cold welding susceptibility testing as part of mechanism qualification using thermal vacuum chambers
- Gaganyaan docking/undocking mechanisms and the proposed Bharatiya Antariksha Station (BAS, target 2035) have complex docking rings and hatches where cold welding analysis is critical
- ISRO's SpadEx mission (Space Docking Experiment) launched December 30, 2024 — successfully demonstrated in-space docking in January 2025; cold welding of docking ring surfaces was a design consideration
UPSC synthesis: Key exam facts: Cold welding = spontaneous bonding of clean metals in hard vacuum = no heat needed = occurs because no oxide layer in vacuum; famous failure = Galileo spacecraft (1991–1995) = high-gain antenna failed to deploy = 3 titanium ribs cold-welded to pins = data transmitted at 1/1000th planned bandwidth; mitigation = dissimilar metals + MoS₂/gold/PTFE coatings + vacuum testing + pyrotechnic backup actuators; ISRO tests mechanisms in thermal vacuum chambers; SpadEx docking experiment = December 30, 2024; BAS target = 2035. Prelims trap: Cold welding does NOT require heat or melting — it occurs at ambient/low temperatures in vacuum (NOT "welding" in the conventional heat-based sense; the "cold" refers to the absence of applied heat, not to temperature of the space environment); cold welding happens because metals lack their protective oxide layer in vacuum (NOT because of extreme cold — spacecraft surfaces can actually get very hot on the sun-facing side); the Galileo high-gain antenna was a titanium rib deployment mechanism (NOT a solar panel — Galileo's solar panels deployed fine; it was the communication antenna that failed).
[Additional] 9b. EV Tribology — How Electric Vehicles Change the Friction Equation
The chapter mentions EVs briefly (fewer moving parts, ~90% motor efficiency) but does not develop the new tribological challenges EVs introduce: ultra-high RPM gearboxes needing electrically non-conductive lubricants, brake corrosion from disuse, and the role of friction in regenerative braking systems.
Key Terms — EV Tribology:
| Term | Meaning |
|---|---|
| Tribology | Science of friction, wear, and lubrication between interacting surfaces — from Greek tribos (rubbing) |
| Regenerative braking | EV braking system where the electric motor runs in reverse as a generator, converting kinetic energy → electrical energy stored back in the battery; friction brakes (disc/drum) engage only for final stop or emergency — reducing brake pad wear and PM2.5 brake dust emissions |
| EV-specific gear oil | Lubricant formulated for EV single-speed reduction gearboxes operating at up to 20,000 RPM and at high voltages; must have low electrical conductivity (high dielectric strength) to prevent arcing between gear surfaces and bearing damage from stray currents |
| PM e-DRIVE scheme | PM Electric Drive Revolution in Innovative Vehicle Enhancement; announced October 2024; budget ₹10,900 crore over FY2025-26 to FY2026-27; targets electric buses, trucks, 2-wheelers, 3-wheelers |
| Brake corrosion (disuse corrosion) | In EVs, friction brakes are rarely engaged (regenerative braking handles most deceleration); brake discs and pads corrode from moisture and road salt without the regular friction that normally keeps them clean; can cause pad seizing or brake fade when emergency braking is needed |
[Additional] EV Tribology — New Friction Challenges in Electric Vehicles (GS3 — Technology / Environment):
ICE vs EV — moving parts and friction interfaces:
| Feature | ICE (Petrol/Diesel) car | Electric Vehicle (EV) |
|---|---|---|
| Moving parts | ~2,000 | ~20 |
| Major friction interfaces | Engine pistons, crankshaft, camshaft, valves, transmission gears, clutch, differential | Motor bearings, single-speed reduction gear, wheel bearings |
| Lubrication needs | Multi-grade engine oil + transmission oil + differential oil = 3+ fluid changes | EV-specific gear oil (rarely changed); motor coolant; no engine oil |
| Brake use | Constant throughout braking | Mostly regenerative braking; friction brakes rarely used |
| Drivetrain efficiency | ~30–40% (ICE) | ~85–95% (electric motor) |
EV-specific tribological challenges:
| Challenge | Detail |
|---|---|
| Ultra-high RPM gearboxes | EV single-speed reduction gearboxes operate at up to 20,000 RPM (vs 5,000–7,000 RPM for ICE transmissions) → increased surface fatigue, heat generation at gear teeth; conventional gear oils insufficient |
| Electrical conductivity of lubricants | High voltages in EV drivetrains can cause stray electrical currents through the lubricant into bearings → electrical discharge machining (EDM) erosion of bearing surfaces; EV gear oils must have high dielectric strength (low electrical conductivity) |
| Brake corrosion from disuse | Regenerative braking handles ~80–90% of deceleration; friction brakes used only for final ~10 km/h and emergencies; discs corrode and pads may seize → potential brake failure in emergency stops |
| Tyre wear increase | EVs are heavier (battery weight) and torque delivery is instant (no gear change delay) → higher tyre wear vs ICE; tyres are THE primary source of brake/tyre PM emissions from EVs |
| Battery thermal management | Li-ion cells generate heat during charge/discharge; immersion cooling uses dielectric fluids that must also lubricate pump components; fluid tribology = growing field |
What regenerative braking IS and IS NOT:
| Regenerative braking IS | Regenerative braking IS NOT |
|---|---|
| Motor running as generator → electromagnetic braking | Friction-based slowing (that's friction brakes) |
| Kinetic energy → electrical energy → battery charge | Energy dissipation as heat |
| The primary braking mechanism in EVs (~80–90% of braking energy) | The only braking mechanism — friction brakes are still present and essential |
| A reason EVs have lower PM2.5 brake dust | A reason EVs have zero tyre wear (tyres still wear — often more than ICE) |
India's EV policy context:
| Scheme | Detail |
|---|---|
| PM e-DRIVE | ₹10,900 crore; October 2024; electric buses + 2W + 3W + trucks; FY2025-26 to FY2026-27 |
| FAME India Phase II (ended) | ₹11,500 crore; ended March 2024; subsidised EV purchase + charging stations |
| EV sales FY 2025-26 | 25,50,865 units (8.64% of overall auto sales; +25.02% YoY) — 2W = 14,72,029 (57.9%); e-4W = 2,22,870 (8.8%, +90.4% YoY); Tata leads e-4W with 38.8% market share (VAHAN dashboard) |
| Major OEMs | Ola Electric (2W), Tata Motors (4W), Mahindra & Mahindra (4W), TVS Motor (2W), Bajaj (3W) |
UPSC synthesis: Key exam facts: EV has ~20 moving parts vs ICE ~2,000; EV gearboxes operate at up to 20,000 RPM (vs 5,000-7,000 ICE); EV gear oil must have high dielectric strength (low conductivity) to prevent electrical arcing in bearings; regenerative braking = motor as generator = kinetic → electrical energy (NOT friction braking); friction brakes still present for emergency/final stop; brake discs corrode in EVs from disuse; tyre wear INCREASES in EVs (heavier + instant torque); PM e-DRIVE = ₹10,900 crore = October 2024; India sold ~1.73 million EVs in FY2024-25. Prelims trap: EVs do NOT eliminate friction entirely — tyres still create rolling/sliding friction with road (how EVs grip, steer, and stop in emergencies); regenerative braking uses electromagnetic induction NOT friction (friction brakes only for emergency/final stop); EVs are often heavier than ICE cars (battery weight) → higher tyre wear (a counterintuitive result — EVs reduce brake dust but can increase tyre particle emissions); the EV-specific gear oil requirement for low electrical conductivity is the key distinction from ICE gear oils.
Exam Strategy
Prelims traps:
- Static friction > kinetic friction for the same pair of surfaces — static friction is higher (it's harder to start motion than maintain it)
- Rolling friction is the least among static, kinetic, and rolling — this is why wheels are so important in transport history
- Vande Bharat is manufactured at ICF Chennai (Integral Coach Factory) — not Rail Coach Factory Kapurthala (which makes LHB coaches); 82 route pairs / 164 services (Feb 2026); first Sleeper rake launched 17 Jan 2026
- MAHSR has 12 stations (not 21) — 4 in Maharashtra, 8 in Gujarat; first operational section Surat–Vapi targeted "around 2027"; full corridor 2028–29; 430 km piers + 341 km girder + 5 km BKC–Shilphata tunnel progress (mid-2026)
- Mumbai-Ahmedabad Bullet Train uses Japan's Shinkansen technology — not France's TGV or Germany's ICE
- Graphite is a dry lubricant (soft layers of carbon slide past each other) — its lubricating property, not its electrical conductivity, is relevant here
- Maglev trains are NOT operational in India as of 2025 — only feasibility studies; do not confuse with metro rail systems which use conventional wheels
Practice Questions
Prelims:
With reference to the Mumbai-Ahmedabad High Speed Rail project, which of the following is/are correct?
- It uses Japan's Shinkansen technology
- It includes an undersea tunnel section under Thane Creek
- It is funded entirely by the Indian government
Select the correct answer:
(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2 and 3
- It uses Japan's Shinkansen technology
Which of the following correctly explains why ball bearings reduce friction in machinery?
(a) They increase the contact area between moving surfaces
(b) They act as a liquid lubricant between surfaces
(c) They replace sliding friction with rolling friction, which is much smaller
(d) They generate a magnetic field that repels the surfaces apart
Mains:
Discuss the significance of India's semi-high-speed rail programme (Vande Bharat Express) for passenger mobility, energy efficiency, and domestic manufacturing capability. What challenges remain in scaling the network? (CSE Mains 2022, GS Paper 3, 15 marks)
Critically examine the potential and limitations of Magnetic Levitation (Maglev) technology for India's future transport needs. (CSE Mains 2024, GS Paper 3, 10 marks)
