RRB Technician Grade III 2024, 2025 PYQs

Concept: Non-uniform motion: unequal distances in equal time intervals.

Solution:

1. Speed keeps changing
2. So distance covered per second is not the same
3. Constant speed / zero acceleration describe uniform motion

Yaad rakhein: Distance–time graph of non-uniform motion is a curve; of uniform motion a straight line.

Answer: (A) Covering unequal distances in equal intervals of time

Concept: Isobars: same mass number, different atomic numbers.

Solution:

1. Same A but different Z → different number of protons
2. So neutrons differ too, and chemical properties differ
3. Example: ⁴⁰Ca (Z = 20) and ⁴⁰Ar (Z = 18)

Trick: isoBARS = same 'Bhaar' (mass); isoTOPES = same 'Place' (Z) in periodic table.

Answer: (C) They have the same number of protons.

Concept: Repeated reflection of sound can guide it to listeners far away.

Solution:

1. Megaphones, shehnai, trumpets send sound in one direction by multiple reflection
2. Curved ceilings and sound boards in halls spread sound evenly
3. Reflection does not change frequency or pitch

Yaad rakhein: Stethoscope also works on multiple reflection of sound.

Answer: (A) Hear sounds clearly over long distances

Concept: Evaporation is a surface phenomenon occurring below boiling point.

Solution:

1. Statement I is the correct definition of evaporation
2. More surface area → more molecules escape → faster evaporation
3. Both statements are true

Yaad rakhein: Evaporation rate rises with surface area, temperature and wind speed; falls with humidity.

Answer: (C) Both statements I and II are true.

Concept: A filament must glow white-hot without melting.

Solution:

1. Tungsten melting point ≈ 3380°C (very high)
2. It also has high resistivity, so it heats up well
3. Bulbs are filled with inert gas (N₂/Ar) to stop its oxidation

Yaad rakhein: Heating elements of heaters use nichrome (alloy) instead.

Answer: (D) It has a very high melting point.

Concept: Add atomic masses of all atoms in the formula.

Solution:

1. Na₂ = $2\times 23=46$
2. C = 12; O₃ = $3\times 16=48$
3. Total = $46+12+48=106$ u

Yaad rakhein: Na₂CO₃·10H₂O is washing soda; anhydrous Na₂CO₃ is soda ash.

Answer: (D) 106 u

Concept: PE at height h = work done against gravity = mgh.

Solution:

1. Lifting needs force equal to weight mg, upward
2. Work = mg × h, done against gravity
3. This work is stored as potential energy

Yaad rakhein: PE depends only on height, not on the path taken.

Answer: (C) Against gravity

Concept: NaHCO₃ is a mild, non-corrosive basic salt.

Solution:

1. Used in baking powder (releases CO₂)
2. Used in antacids (neutralises acid)
3. Used in soda-acid fire extinguishers; it is NOT an acid at all

Yaad rakhein: On heating: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂.

Answer: (C) It is used as a strong acid.

Concept: Mitochondria carry out aerobic respiration and make ATP.

Solution:

1. ATP is the energy currency of the cell
2. Hence mitochondria = powerhouse of the cell
3. Lysosome = suicide bag; ribosome = protein synthesis

Yaad rakhein: Mitochondria have their own DNA and ribosomes.

Answer: (C) Mitochondria

Concept: Xylem and phloem are complex permanent tissues (made of more than one cell type).

Solution:

1. Xylem carries water and minerals
2. Phloem carries food
3. Storage is by parenchyma; protection by epidermis/cork (simple tissues)

Yaad rakhein: Phloem's only dead component is phloem fibres; xylem's only living one is xylem parenchyma.

Answer: (B) Transport of water and food

Concept: At maximum height $v=0$, so $u^2=2gh$.

Solution:

1. $h=1000\text{cm}=10\text{m}$
2. $u^2=2\times 9.8\times 10=196$
3. $u=14$ m/s

Trick: Convert cm to m first — $1000\text{cm}=10\text{m}$.

Answer: (C) 14 m/s

Concept: A net (unbalanced) force produces acceleration, i.e. change in motion.

Solution:

1. It can change speed, direction or both
2. Balanced forces cause no change in motion
3. Mass does not change due to force

Yaad rakhein: Newton's first law: a body keeps its state unless an unbalanced force acts.

Answer: (D) Change in motion

Concept: Air density and refractive index increase towards Earth's surface, bending starlight.

Solution:

1. Starlight bends towards the normal as it goes into denser air
2. Our eye sees it along the bent ray → star looks higher
3. Same effect gives early sunrise and delayed sunset (~2 min)

Yaad rakhein: Twinkling of stars is also due to atmospheric refraction.

Answer: (D) The atmosphere bends the starlight due to gradual changes in refractive index.

Concept: Force $F=q(v\times B)$, so it depends on velocity and on the field B at that point.

Solution:

1. The field of a circular loop varies from point to point
2. So magnitude/direction of force changes with position
3. Force also depends on speed and direction of the charge — not constant or always zero

Yaad rakhein: Force is zero only when v is parallel or antiparallel to B; maximum when perpendicular.

Answer: (B) Depends on position and velocity

Concept: Lymph is like plasma that leaks out of capillaries, with fewer proteins and no RBCs/platelets.

Solution:

1. Lymph contains plasma (water), and WBCs (lymphocytes)
2. Platelets and RBCs are absent in lymph
3. So platelets are present in blood but absent in lymph

Yaad rakhein: Lymph carries digested fats from the intestine (lacteals) and drains excess tissue fluid back into blood.

Answer: (A) Platelets

Concept: –CHO (aldehyde) takes suffix '-al'; C=O in the chain (ketone) takes '-one'.

Solution:

1. CH₃–CH₂–CHO has 3 carbons with –CHO → propanal
2. Propanone is CH₃–CO–CH₃ (acetone), a ketone
3. Statement 1 false, Statement 2 true

Trick: '-CHO' at the end → '-al'; 'C=O' in the middle → '-one'.

Answer: (A) Statement 1 is false but Statement 2 is true.

Concept: Metals and non-metals combine by transfer of electrons, forming ionic bonds.

Solution:

1. Metal loses electrons, non-metal gains → ions (e.g. NaCl, MgO)
2. Sharing occurs between non-metals (covalent)
3. So both statements are false

Trick: Metal + non-metal = transfer = ionic; non-metal + non-metal = sharing = covalent.

Answer: (D) Both statements are false.

Concept: Atomic number Z = number of protons in the nucleus = electrons in a neutral atom.

Solution:

1. O has Z = 8 → 8 protons
2. Neutral atom → 8 electrons (2, 6)
3. Protons are in the nucleus, not in orbits; neutrons in O-16 are 8 but that comes from A − Z

Yaad rakhein: Atomic number is the identity of an element — no two elements have the same Z.

Answer: (A) Oxygen has 8 protons and 8 electrons

Concept: Pressure = Thrust ÷ Area, so smaller area → larger pressure.

Solution:

1. Same force on smaller area → bigger P
2. That is why knives are sharp and nails are pointed
3. Wide straps/tyres spread force to reduce pressure

Yaad rakhein: SI unit of pressure: pascal (Pa) = N/m².

Answer: (D) Larger pressure

Concept: Carbon content increases as plant matter is buried longer and deeper.

Solution:

1. Peat (lowest carbon, ~50–60%)
2. → Lignite (brown coal) → Bituminous
3. → Anthracite (highest carbon, ~90%+, best quality)

Trick: Mnemonic 'P-L-B-A' = 'Please Leave Before Afternoon'.

Answer: (C) Peat → Lignite → Bituminous → Anthracite