General Science
Key Concepts & Formulas
| # | Concept | Quick Explanation |
|---|---|---|
| 1 | Ohm’s Law | V = IR (Voltage = Current × Resistance). Used to calculate electrical properties in railway circuits. |
| 2 | Photosynthesis | 6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂. Plants convert CO₂ and water into glucose using sunlight. |
| 3 | Newton’s 2nd Law | F = ma. Force equals mass times acceleration. Used to calculate train braking distances. |
| 4 | pH Scale | 0-14 scale measuring acidity/alkalinity. 7 is neutral (pure water), <7 acidic, >7 basic. |
| 5 | Human Heart Rate | Normal adult: 72 bpm. Athletes may have 40-60 bpm due to efficient heart function. |
| 6 | Speed Formula | Speed = Distance/Time. Essential for calculating train schedules and average speeds. |
| 7 | Boiling Point Water | 100°C at sea level (1 atm pressure). Decreases at higher altitudes (hill stations). |
10 Practice MCQs
Q1. What is the normal human body temperature? A) 96.4°F B) 98.6°F C) 100.2°F D) 102.4°F
Answer: B) 98.6°F
Solution: Normal human body temperature = 37°C = 98.6°F Conversion: °F = (°C × 9/5) + 32 = (37 × 9/5) + 32 = 98.6°F
Shortcut: Remember “37°C = 98.6°F” as a pair
Concept: General Science - Human Physiology
Q2. Which gas is responsible for photosynthesis? A) CO₂ B) O₂ C) N₂ D) H₂
Answer: A) CO₂
Solution: Plants use CO₂ (carbon dioxide) from air and water to make glucose 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Shortcut: CO₂ in, O₂ out
Concept: General Science - Plant Biology
Q3. What is the pH of pure water? A) 5 B) 6 C) 7 D) 8
Answer: C) 7
Solution: Pure water has pH = 7 (neutral) pH < 7 = acidic, pH > 7 = basic/alkaline
Shortcut: 7 = neutral (like pure water)
Concept: General Science - Chemistry basics
Q4. A train moving at 72 km/h covers how much distance in 30 seconds? A) 200m B) 400m C) 600m D) 800m
Answer: C) 600m
Solution: Speed = 72 km/h = 72 × (1000/3600) = 20 m/s Distance = Speed × Time = 20 m/s × 30 s = 600m
Shortcut: 72 km/h = 20 m/s (divide by 3.6)
Concept: General Science - Physics (Speed conversion)
Q5. If a railway signal uses a 12V battery with 3Ω resistance, what current flows? A) 2A B) 4A C) 6A D) 8A
Answer: B) 4A
Solution: Using Ohm’s Law: I = V/R = 12V/3Ω = 4A
Shortcut: V ÷ R = I (Voltage divided by Resistance)
Concept: General Science - Electricity
Q6. Which vitamin is produced when sunlight hits skin? A) A B) B C) C D) D
Answer: D) D
Solution: Vitamin D is synthesized in skin when exposed to UV-B radiation Essential for calcium absorption and bone health
Shortcut: “D” for Daylight
Concept: General Science - Human Nutrition
Q7. A railway weighbridge shows 50,000 kg. What's its weight in Newtons? (g=10 m/s²) A) 5,000 N B) 50,000 N C) 500,000 N D) 5,00,000 N
Answer: C) 500,000 N
Solution: Weight = Mass × g = 50,000 kg × 10 m/s² = 500,000 N Note: 500,000 N = 5,00,000 N (Indian numbering system)
Shortcut: Add 5 zeroes to kg value (when g=10)
Concept: General Science - Physics (Weight vs Mass)
Q8. If iron rusting is Fe + O₂ → Fe₂O₃, how much rust forms from 112g Fe? (Fe=56) A) 160g B) 320g C) 480g D) 640g
Answer: A) 160g
Solution: 4Fe + 3O₂ → 2Fe₂O₃ 4 × 56g Fe → 2 × 160g Fe₂O₃ 224g Fe → 320g Fe₂O₃ 112g Fe → 160g Fe₂O₃
Shortcut: Half the Fe = Half the product
Concept: General Science - Chemical equations
Q9. A train horn at 340 Hz moves toward station at 34 m/s. What's apparent frequency? (Sound speed = 340 m/s) A) 340 Hz B) 374 Hz C) 408 Hz D) 3740 Hz
Answer: B) 374 Hz
Solution: Doppler effect: f’ = f × (v/(v-vs)) = 340 × (340/(340-34)) = 340 × (340/306) = 374 Hz
Shortcut: Moving source: add 10% when speed is 10% of sound speed
Concept: General Science - Sound waves
Q10. If COVID-19 R0=3 and 1 person infected, how many cases after 3 generations? A) 9 B) 27 C) 81 D) 243
Answer: B) 27
Solution: R0=3 means each infected person infects 3 others Generation 0: 1 Generation 1: 1 × 3 = 3 Generation 2: 3 × 3 = 9 Generation 3: 9 × 3 = 27
Shortcut: R0^n where n = generations (3³ = 27)
Concept: General Science - Disease transmission
5 Previous Year Questions
PYQ 1. Which of the following is NOT a vector quantity? A) Velocity B) Force C) Speed D) Acceleration [RRB NTPC 2021 CBT-1]
Answer: C) Speed
Solution: Speed has magnitude only (scalar) Velocity, Force, Acceleration have both magnitude and direction (vectors)
Exam Tip: Vector = magnitude + direction. Scalar = magnitude only
PYQ 2. The chemical formula of baking soda is: A) NaCl B) NaHCO₃ C) Na₂CO₃ D) NaOH [RRB Group D 2022]
Answer: B) NaHCO₃
Solution: Baking soda = Sodium bicarbonate = NaHCO₃ Used in railway kitchens for cooking and cleaning
Exam Tip: “Bi” in bicarbonate means HCO₃ (one hydrogen)
PYQ 3. Normal blood pressure in humans is: A) 80/120 mmHg B) 90/140 mmHg C) 120/80 mmHg D) 140/90 mmHg [RRB ALP 2018]
Answer: C) 120/80 mmHg
Solution: Normal BP: Systolic 120 mmHg, Diastolic 80 mmHg Format: Systolic/Diastolic (higher/lower)
Exam Tip: Remember 120/80 as “twelve over eighty”
PYQ 4. Which instrument measures atmospheric pressure? A) Barometer B) Hygrometer C) Thermometer D) Anemometer [RRB JE 2019]
Answer: A) Barometer
Solution: Barometer measures air pressure Used in weather stations and railway meteorological departments
Exam Tip: “Bar” = pressure (barometric pressure)
PYQ 5. The disease beriberi is caused by deficiency of: A) Vitamin A B) Vitamin B₁ C) Vitamin C D) Vitamin D [RPF SI 2019]
Answer: B) Vitamin B₁
Solution: Beriberi = Thiamine (Vitamin B₁) deficiency Affects nervous system and heart
Exam Tip: “B” for Beriberi
Speed Tricks & Shortcuts
| Situation | Shortcut | Example |
|---|---|---|
| km/h to m/s | Divide by 3.6 | 72 km/h = 72 ÷ 3.6 = 20 m/s |
| Celsius to Fahrenheit | Double and add 30 | 25°C ≈ 25×2+30 = 80°F (actual: 77°F) |
| pH memory | 7 = neutral, <7 acid, >7 base | Lemon juice pH ≈ 2 (acidic) |
| Water boiling point | 100°C at sea level, drops 1°C per 300m height | At 1500m: ~95°C |
| Human heartbeats | 72 bpm × 60 × 24 = ~1,00,000/day | 1 lakh beats daily |
Common Mistakes to Avoid
| Mistake | Why Students Make It | Correct Approach |
|---|---|---|
| Confusing mass vs weight | Think they’re same | Mass = kg (constant), Weight = N (changes with gravity) |
| Speed vs velocity | Ignore direction | Velocity includes direction, speed doesn’t |
| Mixing up vitamins | Similar names | A-Eyes, B-Energy, C-Cold, D-Bones, K-Clot |
| Celsius vs Kelvin | Forget to add 273 | K = °C + 273 (0°C = 273K) |
| Acid vs base pH | Reverse the scale | pH < 7 = acid, pH > 7 = base |
Quick Revision Flashcards
| Front (Question/Term) | Back (Answer) |
|---|---|
| Normal human body temperature | 37°C or 98.6°F |
| Chemical formula of water | H₂O |
| Speed of sound in air | 343 m/s (at 20°C) |
| pH of stomach acid | 1.5-3.5 |
| Number of bones in adult human | 206 |
| Chemical name of common salt | Sodium chloride (NaCl) |
| Boiling point of water | 100°C at sea level |
| Normal human heart rate | 72 beats per minute |
| Chemical formula of glucose | C₆H₁₂O₆ |
| Percentage of oxygen in air | 21% |
Topic Connections
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Direct Link: General Science connects to Current Affairs (new scientific discoveries), Geography (weather patterns, natural phenomena), and Economics (healthcare costs, agricultural science)
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Combined Questions: Science + History (inventions timeline), Science + Polity (health policies), Science + Geography (climate change, natural resources)
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Foundation For: Technical posts (RRB JE, ALP) require deeper physics/chemistry, Medical standards for RPF posts, Environmental policies for Group D sustainability initiatives
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