General Science — UP Police Constable Study Notes

Overview

General Science forms a significant portion of the General Knowledge section in UP Police Constable exam, typically accounting for 8-12 questions. This section tests your understanding of fundamental scientific principles from Physics, Chemistry and Biology, with emphasis on everyday applications rather than advanced theory. Questions are straightforward and focus on concepts taught up to Class 10 level, covering topics like motion, energy, chemical reactions, human body systems, diseases and nutrition.

The exam expects factual recall combined with practical understanding — you should know not just what happens but why common phenomena occur. For instance, understanding why ice floats on water, how vaccines work, or what causes rusting. The key to scoring well is consistent revision of basic concepts, memorizing important facts (vitamins, diseases, SI units) and connecting scientific principles to daily life observations. Most questions are direct and can be answered quickly if you have solid foundational knowledge.

Focus on high-yield topics: human body systems (especially digestive, circulatory and respiratory), diseases and their causative agents, vitamins and deficiencies, basic laws of motion and energy, chemical reactions in daily life, and properties of matter. Avoid going too deep into any single area — breadth of coverage matters more than depth for this exam.

Key Concepts

• **States of Matter**: Matter exists in solid, liquid, gas and plasma states. Solids have fixed shape and volume; liquids have fixed volume but take container shape; gases have neither fixed shape nor volume. Changes between states involve heat energy (melting, freezing, evaporation, condensation, sublimation).

• **Laws of Motion**: Newton's three laws govern movement — objects remain at rest/motion unless acted upon by force; force equals mass times acceleration (F = ma); every action has equal and opposite reaction. These explain everyday phenomena like seat belts, rocket propulsion and recoil of guns.

• **Energy Conservation**: Energy cannot be created or destroyed, only converted from one form to another. Common conversions include electrical to light (bulb), chemical to mechanical (engine), solar to electrical (solar panel) and potential to kinetic (falling object).

• **Acids, Bases and Salts**: Acids taste sour, turn blue litmus red and have pH < 7 (HCl, H₂SO₄). Bases taste bitter, turn red litmus blue and have pH > 7 (NaOH, Ca(OH)₂). Neutralization produces salt and water. pH 7 is neutral (pure water).

• **Cell Structure**: Cell is the basic unit of life. Plant cells have cell wall, chloroplasts and large vacuole; animal cells lack these. Nucleus controls cell activities, mitochondria produce energy, ribosomes synthesize proteins and chloroplasts perform photosynthesis in plants.

• **Human Body Systems**: Digestive system breaks down food (mouth → stomach → small intestine → large intestine). Circulatory system transports blood (heart pumps blood through arteries and veins). Respiratory system exchanges gases (lungs absorb oxygen, expel carbon dioxide). Nervous system coordinates body functions through brain, spinal cord and nerves.

• **Diseases and Immunity**: Communicable diseases spread through pathogens — bacteria (tuberculosis, typhoid), viruses (dengue, COVID-19), protozoa (malaria) and fungi (ringworm). Non-communicable diseases don't spread (diabetes, cancer, heart disease). Vaccines provide immunity by introducing weakened pathogens.

• **Nutrition**: Carbohydrates and fats provide energy; proteins build and repair tissues; vitamins and minerals regulate body functions; water is essential for all life processes. Balanced diet contains all nutrients in proper proportion.

Key Facts

**Physics Fundamentals** • SI unit of force: Newton (N); Work and Energy: Joule (J); Power: Watt (W); Pressure: Pascal (Pa) • Speed of light: 3 × 10⁸ m/s; Speed of sound in air: 340 m/s at room temperature • Concave mirrors converge light (used in shaving mirrors, torches); convex mirrors diverge light (used in vehicle rear-view mirrors) • Electric current flows from positive to negative terminal; measured in Ampere (A); resistance in Ohm (Ω)

**Chemistry Essentials** • Atomic number = number of protons; Mass number = protons + neutrons • Metals are malleable, ductile, conduct heat/electricity; Non-metals are brittle, poor conductors (except graphite) • Common acids: HCl (hydrochloric), H₂SO₄ (sulfuric), HNO₃ (nitric), CH₃COOH (acetic/vinegar) • Rusting of iron requires oxygen and moisture; prevented by painting, oiling or galvanization

**Biology Must-Know Facts** • Human blood groups: A, B, AB (universal recipient), O (universal donor); Rh factor: positive or negative • Normal human body temperature: 37°C (98.6°F); Blood pressure: 120/80 mmHg • Photosynthesis equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight and chlorophyll) • DNA (deoxyribonucleic acid) carries genetic information; double helix structure discovered by Watson and Crick

**Vitamins and Deficiency Diseases** • Vitamin A: Night blindness; found in carrots, milk, eggs • Vitamin B₁ (Thiamine): Beri-beri; found in grains, pulses • Vitamin C (Ascorbic acid): Scurvy; found in citrus fruits, amla • Vitamin D: Rickets (children), osteomalacia (adults); sunlight exposure, fish oil • Vitamin K: Blood clotting problems; green leafy vegetables

Worked Examples

**Example 1: Motion and Speed** Question: A car travels 300 km in 5 hours. What is its average speed?

Solution: Average speed = Total distance / Total time = 300 km / 5 hours = 60 km/h

Remember: Speed is always distance divided by time. Don't confuse with velocity (which includes direction).

**Example 2: pH and Neutralization** Question: If a solution has pH 3, it is: (a) Strongly basic (b) Weakly basic (c) Strongly acidic (d) Neutral

Solution: pH scale ranges from 0-14. pH < 7 indicates acid, pH = 7 is neutral, pH > 7 is base. pH 3 is well below 7, indicating strong acidity.

Answer: (c) Strongly acidic

Tip: Lower the pH value, stronger the acid. HCl (stomach acid) has pH 1-2; lemon juice has pH 2-3.

**Example 3: Blood Circulation** Question: Which blood vessel carries oxygenated blood from lungs to heart?

Solution: Blood circulation pathway:

• Deoxygenated blood: Heart (right side) → Pulmonary artery → Lungs
• Oxygenated blood: Lungs → Pulmonary vein → Heart (left side) → Body

Answer: Pulmonary vein

Common confusion: Students often think arteries always carry oxygenated blood, but pulmonary artery carries deoxygenated blood to lungs. Remember the exception.

Common Mistakes

**Confusing mass and weight** → Mass is amount of matter (measured in kg, constant everywhere); weight is force due to gravity (measured in Newton, varies with location). On moon, your mass stays same but weight becomes 1/6th of Earth weight.

**Mixing up real and virtual images** → Real images can be projected on screen (formed by concave mirrors and convex lenses); virtual images cannot be projected (formed by plane mirrors, convex mirrors and concave lenses). Virtual images appear behind the mirror/lens.

**Believing all bacteria cause diseases** → Many bacteria are beneficial. Lactobacillus in curd aids digestion, nitrogen-fixing bacteria in soil help plants, bacteria decompose waste. Only pathogenic bacteria cause diseases like tuberculosis, cholera and typhoid.

**Thinking boiling and evaporation are same** → Boiling occurs throughout liquid at fixed temperature (100°C for water at normal pressure); evaporation occurs only at surface at any temperature. Clothes dry due to evaporation, not boiling.

**Confusing vitamins with minerals** → Vitamins are organic compounds (A, B, C, D, E, K); minerals are inorganic elements (iron, calcium, iodine, sodium). Both are micronutrients needed in small amounts. Iron deficiency causes anemia; iodine deficiency causes goiter.

Quick Reference

• Force = mass × acceleration; Pressure = Force / Area; Work = Force × Distance

• Conductors allow electricity flow (copper, silver, aluminum); Insulators resist flow (rubber, wood, plastic)

• Arteries carry blood away from heart (thick walls); Veins carry blood toward heart (thin walls, have valves)

• Communicable diseases spread (TB, malaria, dengue); Non-communicable don't spread (diabetes, cancer)

• Carbohydrates = 4 cal/g, Proteins = 4 cal/g, Fats = 9 cal/g (highest energy source)

• Photosynthesis in plants produces oxygen; Respiration in all living beings consumes oxygen and releases CO₂