General Science — Study Notes for Maharashtra Police Bharti
Overview
General Science is a high-scoring section in the Maharashtra Police Bharti exam because questions are typically fact-based and straightforward. The syllabus covers fundamental concepts from Physics, Chemistry, and Biology that you encountered in school (Classes 6–10 level). Examiners test whether you understand everyday scientific phenomena — why the sky is blue, how vaccines work, what makes iron rust.
Most are direct recall, but some require applying a concept to a practical situation. Mastering the basics here gives you quick, easy marks that balance tougher reasoning or maths questions.
Focus areas: units and measurements, laws of motion, light and sound, acids-bases-salts, metals and non-metals, human body systems, diseases, and nutrition. Connect each concept to real-life examples — that's how questions are framed.
Key Concepts
Physics
- Newton's Laws of Motion: First law (inertia), second law (F = ma), third law (action-reaction). Every motion question traces back here.
- Work, Energy, Power: Work = Force × Distance. Energy cannot be created or destroyed, only transformed. Power = Work / Time.
- Light: Travels in straight lines, reflects (mirror), refracts (lens). White light splits into VIBGYOR via a prism.
- Sound: Needs a medium; cannot travel in vacuum. Speed in air ≈ 343 m/s. Echoes need minimum 17 m distance.
- Electricity: Current (I) = Charge / Time. Ohm's Law: V = I × R. Series vs parallel circuits.
Chemistry
- Atoms & Molecules: Atom is the smallest particle retaining element identity. Molecule is two or more atoms bonded.
- Acids, Bases, Salts: Acids taste sour, turn blue litmus red; bases taste bitter, turn red litmus blue. pH 7 = neutral.
- Metals vs Non-metals: Metals are lustrous, good conductors, malleable. Non-metals are brittle, poor conductors.
- Chemical Reactions: Combination, decomposition, displacement, double displacement, oxidation-reduction (redox).
Biology
- Cell: Basic unit of life. Plant cells have cell wall; animal cells do not. Mitochondria = powerhouse.
- Human Body Systems: Digestive, respiratory, circulatory, nervous, excretory — know one key organ and function for each.
- Diseases: Differentiate bacterial (typhoid, TB), viral (COVID, dengue), and deficiency diseases (scurvy, rickets).
- Nutrition: Carbohydrates, proteins, fats, vitamins, minerals, water. Know sources and deficiency effects.
Formulas / Key Facts
Physics Formulas
| Quantity | Formula | Unit |
|---|---|---|
| Speed | Distance / Time | m/s |
| Acceleration | (v − u) / t | m/s² |
| Force | Mass × Acceleration | Newton (N) |
| Work | Force × Distance | Joule (J) |
| Power | Work / Time | Watt (W) |
| Density | Mass / Volume | kg/m³ |
| Ohm's Law | V = I × R | Volt, Ampere, Ohm |
Must-Remember Facts
- Speed of light in vacuum = 3 × 10⁸ m/s (fastest in universe).
- Normal human body temperature = 37°C or 98.6°F.
- pH of human blood = 7.35–7.45 (slightly alkaline).
- Largest organ of human body = Skin; largest internal organ = Liver.
- Photosynthesis equation: 6CO₂ + 6H₂O + Sunlight → C₆H₁₂O₆ + 6O₂.
- Universal solvent = Water.
- Hardest natural substance = Diamond (carbon allotrope).
- Vitamin C deficiency = Scurvy; Vitamin D deficiency = Rickets.
- Blood group that can donate to all = O (universal donor); can receive from all = AB (universal recipient).
- SI unit of electric current = Ampere (A).
Worked Examples
Example 1 — Physics (Motion)
Question: A car travels 150 km in 3 hours. What is its average speed?
Solution:
- Speed = Distance / Time
- Speed = 150 km / 3 h = 50 km/h
Answer: 50 km/h
Example 2 — Chemistry (pH Concept)
Question: A solution turns red litmus blue. Is it acidic, basic, or neutral?
Solution:
- Red litmus turning blue indicates the presence of a base (alkaline substance).
- Acids turn blue litmus red; neutral solutions cause no change.
Answer: Basic (alkaline)
Example 3 — Biology (Disease Identification)
Question: Night blindness is caused by deficiency of which vitamin?
Solution:
- Night blindness = difficulty seeing in low light.
- Caused by lack of Vitamin A, which is essential for rhodopsin production in the retina.
- Sources of Vitamin A: carrot, papaya, fish liver oil, milk.
Answer: Vitamin A
Common Mistakes
- Confusing mass and weight
- Wrong: "Mass changes on the Moon."
- Correct: Mass remains constant everywhere; weight (force due to gravity) changes with location.
- Mixing up arteries and veins
- Wrong: "Veins carry oxygenated blood."
- Correct: Arteries carry blood away from heart (usually oxygenated); veins carry blood toward heart (usually deoxygenated). Exception: pulmonary vessels.
- Believing sound travels in vacuum
- Wrong: "Sound travels fastest in vacuum."
- Correct: Sound requires a medium. It travels fastest in solids, slower in liquids, slowest in gases, and not at all in vacuum.
- Confusing atomic number and mass number
- Wrong: "Atomic number = protons + neutrons."
- Correct: Atomic number = number of protons only. Mass number = protons + neutrons.
- Forgetting that rusting needs both oxygen AND moisture
- Wrong: "Iron rusts in dry air."
- Correct: Rusting (iron + oxygen + water → iron oxide) requires moisture. Dry air alone will not rust iron.
Quick Reference
- Newton's 3rd Law: Every action has an equal and opposite reaction.
- Ohm's Law: V = I × R (Voltage = Current × Resistance).
- Photosynthesis occurs in: Chloroplast (green pigment = chlorophyll).
- RBC lifespan: ~120 days; produced in bone marrow.
- Acid + Base → Salt + Water (neutralisation reaction).
- Unit of frequency: Hertz (Hz); human hearing range = 20 Hz to 20,000 Hz.
Revise these facts weekly. Link each concept to a real-life example — exam questions often describe a situation rather than ask directly. Good luck!