RRB Technician Grade III 2024, 2025 PYQs

Concept: Work is done when a force acts on an object and the object is displaced in the direction of the force: $W=F\times s$.

1. Force is applied and the object moves horizontally, so $s\ne 0$.
2. Hence $W=F\times s\ne 0$ – work is done by the force.
3. Force never changes mass or inertia of a body.

Yaad rakhein: Two conditions for work: a force acts and displacement occurs.

Answer: (A) Work is done by the force.

Concept: Plant hormones (auxin, gibberellin, cytokinin, abscisic acid) coordinate growth, development and responses to the environment.

1. Cytokinins actually promote cell division – so statement A is wrong.
2. Abscisic acid inhibits growth while the others promote growth – statement B is correct.
3. Statements C and D are correct roles of hormones.

Yaad rakhein: Cytokinin = cell division; Auxin = cell elongation; Gibberellin = stem growth; ABA = growth inhibitor (wilting).

Answer: (A) All plant hormones except cytokinins promote cell division.

Concept: Laws of refraction: (1) incident ray, refracted ray and normal lie in the same plane; (2) Snell's law $\frac{\sin i}{\sin r}=\text{constant}$.

1. Statement A says they do NOT lie in the same plane – false.
2. Statement B is Snell's law for a given colour and pair of media – true.
3. So A is false and B is true.

Yaad rakhein: The constant $\frac{\sin i}{\sin r}$ is the refractive index of the second medium w.r.t. the first.

Answer: (B) 'A' is false and 'B' is true.

Concept: Refractive index of medium 2 w.r.t. medium 1: $n_{21}=\frac{v_1}{v_2}$ (ratio of speeds of light).

1. Light changes speed when it passes from one medium to another.
2. Refractive index compares these speeds: $n=\frac{c}{v}$ for absolute refractive index.
3. Frequency of light does not change on refraction, so option A is wrong.

Yaad rakhein: Larger refractive index = optically denser = slower light.

Answer: (C) the speed of propagation of light in two different media

Concept: Gravity on the Moon is about $\frac{1}{6}$ of that on the Earth, so weight on the Moon $=\frac{1}{6}\times$ weight on the Earth.

1. Weight on the Earth $=60\text{N}$.
2. Weight on the Moon $=\frac{60}{6}=10\text{N}$.
3. Mass stays the same; only weight changes.

Trick: Moon weight = Earth weight $÷6$.

Answer: (A) 10 N

Concept: The aperture of a spherical mirror is the diameter of its reflecting surface (MN in the figure).

1. P = pole, C = centre of curvature, F = focus.
2. The circular outline of the reflecting surface has a diameter MN – this is the aperture.
3. Distance CF is $\frac{R}{2}$ (equal to $f$), not the aperture.

Yaad rakhein: Aperture = size of the reflecting surface; Focal length $f=\frac{R}{2}$.

Answer: (C) the diameter of the reflecting surface of the mirror

Concept: Metals combine with oxygen of air to form metal oxides.

1. Metal + oxygen $\to$ metal oxide.
2. Example: $2\mathrm{C}\mathrm{u}+{\mathrm{O}}_2\to 2\mathrm{C}\mathrm{u}\mathrm{O}$ (black).
3. Example: $4\mathrm{A}\mathrm{l}+3{\mathrm{O}}_2\to 2\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$; metal oxides are mostly basic.

Yaad rakhein: Metal oxides are basic; non-metal oxides are acidic.

Answer: (B) Metal oxide

Concept: In a combination reaction two or more reactants combine to form a single product.

1. Coal is mainly carbon.
2. On burning: $\mathrm{C}(\mathrm{s})+{\mathrm{O}}_2(\mathrm{g})\to \mathrm{C}{\mathrm{O}}_2(\mathrm{g})$ + heat.
3. Two reactants give one product, so it is a combination (also exothermic) reaction.

Trick: Many reactants $\to$ one product = combination; one reactant $\to$ many products = decomposition.

Answer: (D) Combination reaction

Concept: A solenoid is a long coil of many circular turns of insulated wire.

1. Inside the solenoid the field lines are parallel straight lines – a uniform field.
2. One end behaves like a north pole and the other like a south pole.
3. This pattern is the same as the field of a bar magnet.

Yaad rakhein: Current-carrying solenoid = bar magnet; with a soft iron core it becomes an electromagnet.

Answer: (C) bar magnet

Concept: Each cell organelle has a specific function in the cell.

1. Cell wall gives plants structural strength: 1-b.
2. Ribosomes are sites of protein synthesis: 2-c.
3. Lysosomes digest foreign matter and worn-out parts (suicide bags): 3-a.
4. Golgi apparatus packages materials and helps form lysosomes: 4-d.

Yaad rakhein: Lysosome = suicide bag; Ribosome = protein factory; Mitochondria = powerhouse.

Answer: (A) 1-b, 2-c, 3-a, 4-d

Concept: An acid reacts with a base to give salt and water; this is neutralisation.

1. Acid + base $\to$ salt + water.
2. Example: $\mathrm{H}\mathrm{C}\mathrm{l}+\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}\to \mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}+{\mathrm{H}}_2\mathrm{O}$.
3. The ${\mathrm{H}}^{+}$ of acid and $\mathrm{O}{\mathrm{H}}^{-}$ of base combine to form water; heat is released.

Yaad rakhein: Neutralisation is exothermic; antacids neutralise excess stomach acid.

Answer: (D) neutralisation reaction

Concept: Barium chloride and sodium sulphate undergo double displacement, forming an insoluble precipitate.

1. $\mathrm{N}{\mathrm{a}}_2\mathrm{S}{\mathrm{O}}_4(\mathrm{a}\mathrm{q})+\mathrm{B}\mathrm{a}\mathrm{C}{\mathrm{l}}_2(\mathrm{a}\mathrm{q})\to \mathrm{B}\mathrm{a}\mathrm{S}{\mathrm{O}}_4(\mathrm{s})+2\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})$.
2. $\mathrm{B}\mathrm{a}\mathrm{S}{\mathrm{O}}_4$ is insoluble in water.
3. It appears as a white precipitate.

Yaad rakhein: $\mathrm{B}\mathrm{a}\mathrm{S}{\mathrm{O}}_4$ – white ppt; $\mathrm{P}\mathrm{b}{\mathrm{I}}_2$ – yellow ppt; $\mathrm{C}\mathrm{u}(\mathrm{O}\mathrm{H}{)}_2$ – blue ppt.

Answer: (A) White precipitate of ${\text{BaSO}}_4$

Concept: Atomic mass unit (u) $=\frac{1}{12}$ of the mass of a carbon-12 atom. Atomic mass ≈ protons + neutrons.

1. Sodium: atomic number $11$ (protons $=11$).
2. Neutrons $=12$.
3. Mass $=11+12=23\text{u}$.

Yaad rakhein: Na: atomic number $11$, mass $23\text{u}$; don't confuse the two.

Answer: (A) 23u

Concept: In budding, a new individual develops as an outgrowth (bud) from the parent body.

1. Hydra has regenerative cells that divide repeatedly at one site.
2. This forms a bud that grows into a tiny Hydra and detaches when mature.
3. Spirogyra – fragmentation; Planaria – regeneration; Amoeba – binary fission.

Yaad rakhein: Hydra uses regenerative cells for budding; yeast also buds.

Answer: (B) Hydra

Concept: Fungi like Rhizopus (bread mould) reproduce by spore formation.

1. Thread-like hyphae bear tiny blob-on-a-stick structures.
2. These blobs are sporangia, containing cells (spores) that grow into new Rhizopus.
3. Spores have thick walls that protect them until they reach a moist surface.

Yaad rakhein: Rhizopus – sporangia; spores spread by air.

Answer: (B) Sporangia

Concept: $W=F\times s$; if displacement is zero, no work is done.

1. Force $F=1\text{N}$.
2. The rock does not move, so $s=0$.
3. $W=1\times 0=0\text{J}$.

Trick: No displacement $\Rightarrow$ zero work, however tired you get.

Answer: (C) 0 J

Concept: Ozone (${\mathrm{O}}_3$) is a molecule of three oxygen atoms.

1. (i) True – ${\mathrm{O}}_3$ has three O atoms.
2. (ii) True – ${\mathrm{O}}_2$ is needed by all aerobic organisms.
3. (iii) False – ozone is a deadly poison at ground level; in the upper atmosphere it shields us from UV rays.

Yaad rakhein: Ozone is depleted by CFCs; it absorbs harmful UV radiation.

Answer: (A) Only (i) and (ii)

Concept: Biodegradable substances are broken down by microbes (bacteria, fungi); non-biodegradable ones are not.

1. Vegetable peels – decomposed by microbes: biodegradable.
2. Spoilt food – decomposed: biodegradable.
3. Plastic bottles – not broken down by microbes: non-biodegradable.

Yaad rakhein: Plastic, glass, DDT, metals – non-biodegradable.

Answer: (A) Only B

Concept: Thomson proposed that an atom is a positively charged sphere with electrons embedded in it.

1. Positive charge = red edible part of the watermelon.
2. Electrons = seeds embedded in it.
3. The atom is electrically neutral as charges are equal. Also called the plum pudding / Christmas pudding model.

Yaad rakhein: Thomson – watermelon / plum pudding; Rutherford – nuclear model; Bohr – fixed orbits.

Answer: (C) Watermelon

Concept: Complex permanent tissues are made of more than one type of cell working together, e.g. xylem and phloem.

1. A, B and D are true: many cell types, common function, vascular bundles.
2. Parenchyma and collenchyma are simple permanent tissues (one cell type).
3. So statement C is incorrect.

Yaad rakhein: Simple: parenchyma, collenchyma, sclerenchyma; Complex: xylem, phloem.

Answer: (C) Complex tissue includes parenchyma and collenchyma.