BD Police Constable Written cheat sheet
BD Police Constable Written · Keep the key ideas within reach.
Bengali Language and Literature
বাংলা বর্ণমালায় স্বরবর্ণ ১১টি এবং ব্যঞ্জনবর্ণ ৩৯টি; মোট ৫০টি বর্ণ।
স্বরবর্ণ ১১টি: অ আ ই ঈ উ ঊ ঋ এ ঐ ও ঔ; ব্যঞ্জনবর্ণে অন্তর্স্থ ৪টি (য র ল ব) ও উষ্ম ৪টি (শ ষ স হ)।
বাংলা ভাষায় কার-চিহ্ন ১০টি (া ি ী ু ূ ৃ ে ৈ ো ৌ); অ-কার কোনো চিহ্ন ছাড়াই লেখা হয়।
বাংলা ভাষায় মৌলিক শব্দভাণ্ডার তিন উৎসের: তৎসম, তদ্ভব ও অর্ধতৎসম; এছাড়া দেশি ও বিদেশি শব্দ আছে।
সন্ধি প্রধানত দুই প্রকার: স্বরসন্ধি ও ব্যঞ্জনসন্ধি; বিসর্গসন্ধি ব্যঞ্জনসন্ধির অন্তর্ভুক্ত।
সমাস প্রধানত ছয় প্রকার: দ্বন্দ্ব, কর্মধারয়, তৎপুরুষ, বহুব্রীহি, দ্বিগু ও অব্যয়ীভাব।
কারক ছয় প্রকার: কর্তৃ, কর্ম, করণ, সম্প্রদান, অপাদান ও অধিকরণ; বিভক্তি সাতটি (প্রথমা থেকে সপ্তমী)।
বাংলা সাহিত্যের আদি নিদর্শন চর্যাপদ; এটি বৌদ্ধ সহজিয়া সিদ্ধাচার্যদের রচনা, হরপ্রসাদ শাস্ত্রী মহাশয় ১৯০৭ সালে আবিষ্কার করেন।
মধ্যযুগে শ্রীকৃষ্ণকীর্তন (বড়ু চণ্ডীদাস), মঙ্গলকাব্য ও বৈষ্ণব পদাবলি প্রধান; আধুনিক যুগের সূচনা মাইকেল মধুসূদন দত্তের হাত ধরে।
রবীন্দ্রনাথ ঠাকুর ১৯১৩ সালে গীতাঞ্জলি কাব্যের ইংরেজি অনুবাদের জন্য সাহিত্যে নোবেল পুরস্কার পান; তিনিই প্রথম এশীয় নোবেলজয়ী।
English Language
Parts of speech are eight: noun, pronoun, adjective, verb, adverb, preposition, conjunction, interjection.
Present perfect = have/has + past participle; it links a past action to the present and rejects definite past time markers such as yesterday.
Passive voice = form of be + past participle; the object of the active sentence becomes the subject.
Reported speech shifts tense one step back (present to past, past to past perfect) unless the reporting verb is present or the statement is a universal truth.
Conditional type 1 = if + present simple, will + base verb; type 2 = if + past simple, would + base verb; type 3 = if + past perfect, would have + past participle.
Articles: 'a' before consonant sounds, 'an' before vowel sounds, 'the' for definite or unique reference; no article before uncountable nouns used generally.
Prepositions of time: at for clock times, on for days and dates, in for months, years and longer periods.
Subject-verb agreement: each, every, either, neither, anyone, everyone take a singular verb; collective nouns take singular verbs when acting as one unit.
Common confusions: affect (verb) vs effect (noun); its (possessive) vs it's (it is); principal (chief) vs principle (rule).
Idioms: 'once in a blue moon' means very rarely; 'to beat about the bush' means to avoid the main point; 'a bolt from the blue' means a sudden shock.
Mathematics
Average of n numbers = sum of numbers / n; sum = average x n.
Speed = distance / time; to convert km/h to m/s multiply by 5/18, and m/s to km/h multiply by 18/5.
Simple interest = (P x R x T)/100; amount = P + SI.
Compound amount = P(1 + R/100)^n; compound interest = amount minus principal.
Profit percent = (profit/cost price) x 100; selling price = cost price x (100 + profit%)/100.
Area formulas: rectangle = length x breadth; triangle = 1/2 x base x height; circle = pi x r^2; trapezium = 1/2 x (sum of parallel sides) x height.
Pythagoras theorem: in a right triangle, hypotenuse^2 = base^2 + perpendicular^2.
Sum of first n natural numbers = n(n+1)/2; sum of squares = n(n+1)(2n+1)/6.
Percentage change = (change/original) x 100; successive discounts of a% and b% equal a single discount of a + b - ab/100 percent.
LCM x HCF = product of the two numbers; time-and-work uses rate = 1/days and adds rates for workers together.
General Knowledge (Bangladesh and International Affairs)
Bangladesh became independent on 26 March 1971; Victory Day is 16 December 1971; the surrender ceremony was held at the Race Course Maidan, Dhaka.
The Constitution of Bangladesh took effect on 16 December 1972; it originally had 4 fundamental principles: nationalism, socialism, democracy and secularism.
Bangladesh has 8 divisions, 64 districts and 495 upazilas; the capital is Dhaka and the currency is the taka.
The national anthem 'Amar Shonar Bangla' was written by Rabindranath Tagore; the national poet is Kazi Nazrul Islam.
The Jatiya Sangsad has 350 seats: 300 general and 50 reserved for women; members serve five-year terms.
The Sundarbans, the world's largest mangrove forest, is a UNESCO World Heritage Site; the Royal Bengal Tiger is the national animal.
The United Nations was founded on 24 October 1945; its headquarters is in New York and Bangladesh joined in 1974.
The UN Security Council has 5 permanent members (China, France, Russia, UK, USA) with veto power and 10 non-permanent members elected for two years.
SAARC was founded in 1985 in Dhaka; its secretariat is in Kathmandu, Nepal.
The Universal Declaration of Human Rights was adopted on 10 December 1948; Human Rights Day is observed on that date.
Basic Computer Knowledge
1 byte = 8 bits; 1 kilobyte = 1024 bytes; 1 megabyte = 1024 KB; 1 gigabyte = 1024 MB.
RAM is volatile working memory; ROM is non-volatile and retains firmware such as the BIOS.
The CPU has three main units: arithmetic logic unit, control unit and registers; it executes instructions in fetch-decode-execute cycles.
Input devices include keyboard, mouse, scanner and microphone; output devices include monitor, printer and speaker.
Software divides into system software (operating systems, device drivers) and application software (word processors, browsers).
Shortcuts: Ctrl+C copy, Ctrl+V paste, Ctrl+X cut, Ctrl+Z undo, Ctrl+S save, Ctrl+P print, Ctrl+A select all.
An IP address identifies a device on a network; IPv4 is 32-bit and IPv6 is 128-bit.
HTTP transfers web pages; HTTPS adds encryption; URL is the address of a resource on the web.
A firewall filters network traffic by rules; antivirus software detects malicious code; both are security tools, not storage tools.
Binary uses base 2, decimal base 10, octal base 8 and hexadecimal base 16; hexadecimal digits run 0-9 and A-F.
Physics, Chemistry and General Science
Newton's three laws: inertia; F = ma; every action has an equal and opposite reaction.
Speed of light in vacuum is about 3 x 10^8 m/s; speed of sound in air is about 343 m/s at room temperature.
Work = force x displacement; power = work/time; SI unit of power is the watt.
Ohm's law: V = IR; electric power P = VI = I^2R = V^2/R.
Density = mass/volume; relative density has no unit; an object floats if its density is less than the liquid's.
Atomic number = number of protons; mass number = protons + neutrons; isotopes have equal protons but different neutrons.
pH below 7 is acidic, 7 is neutral, above 7 is basic; litmus turns red in acid and blue in base.
Photosynthesis: 6CO2 + 6H2O + light energy gives C6H12O6 + 6O2, occurring in chloroplasts with chlorophyll.
Human blood groups follow the ABO and Rh systems; O negative is the universal donor and AB positive the universal recipient.
Newton's law of gravitation: F = G m1 m2 / r^2; acceleration due to gravity on Earth is about 9.8 m/s^2.
Geography
Earth's layers: crust, mantle, outer core and inner core; the crust is thinnest under oceans and thickest under mountains.
Latitude lines run east-west and measure distance north or south of the equator (0 to 90 degrees); longitude lines run pole to pole and measure 0 to 180 degrees east or west of Greenwich.
The Tropic of Cancer is at 23.5 degrees north and the Tropic of Capricorn at 23.5 degrees south; the equator is 0 degrees.
Earth rotates on its axis once in about 24 hours causing day and night; it revolves around the Sun in about 365.25 days causing seasons.
Rivers of Bangladesh: the Padma, Meghna and Jamuna form the main delta system; the Padma is the lower course of the Ganges.
Mount Everest (8,848 m) is the highest peak; the Dead Sea shore is the lowest land point on Earth's surface.
The Pacific is the largest and deepest ocean; the Mariana Trench is its deepest point.
Climate zones: tropical, subtropical, temperate, polar; Bangladesh has a tropical monsoon climate with hot, rainy and cool seasons.
Maps use scale to relate map distance to ground distance; contour lines join points of equal elevation.
The Sahara is the largest hot desert; the Nile is traditionally ranked the longest river in Africa.
Environment and Disaster Management
Greenhouse gases include carbon dioxide, methane, nitrous oxide and water vapour; they trap outgoing infrared radiation and warm the surface.
Global warming refers to the rise in average global temperature; climate change includes that plus shifts in rainfall, sea level and extreme events.
Ozone in the stratosphere absorbs ultraviolet radiation; depletion is driven mainly by chlorofluorocarbons.
The 3Rs of waste management are reduce, reuse and recycle, in that order of priority.
Bangladesh's cyclone seasons are pre-monsoon (April-May) and post-monsoon (October-November); the Bay of Bengal's shallow shelf intensifies storm surges.
Cyclone warning signals are numbered 1 to 10, with higher numbers indicating greater danger; signal 10 is the most severe.
The Bangladesh Meteorological Department issues weather and cyclone warnings; the Cyclone Preparedness Programme handles community evacuation.
Flood types include river flood, flash flood, tidal surge and urban waterlogging; embankments and early warning reduce loss.
Earthquake magnitude is measured on the Richter scale (logarithmic); intensity is described by the Modified Mercalli scale.
Disaster management cycle phases: mitigation, preparedness, response and recovery; mitigation and preparedness occur before the event.
General Knowledge (Bangladesh and International Affairs)
Bangladesh's national flag is green with a red circle; green stands for the land and red for the blood of the liberation war.
The national emblem of Bangladesh features a water lily flanked by rice sheaves and jute leaves, with four stars above.
The first President of Bangladesh was Sheikh Mujibur Rahman; the Mujibnagar Government was formed in April 1971.
Bangabandhu Satellite-1, launched in May 2018, is Bangladesh's first communications satellite.
The World Bank, IMF and WHO are UN specialised agencies; the WTO, established in 1995, replaced GATT.
ASEAN was founded in 1967 in Bangkok with five founding members; its secretariat is in Jakarta.
The European Union's common currency is the euro; not all member states use it.
The Nobel Prizes were established by Alfred Nobel's will; the Peace Prize is awarded in Oslo, Norway, and the others in Stockholm, Sweden.
The Olympic Games are held every four years; the Summer and Winter Games are now held in alternating even years.
The Commonwealth is a voluntary association of mostly former British territories; its secretariat is in London.
Physics, Chemistry and General Science
States of matter: solid has fixed shape and volume; liquid has fixed volume but takes container shape; gas fills any container.
Heat transfer occurs by conduction (solids), convection (fluids) and radiation (no medium needed; this is how the Sun's heat reaches Earth).
Sound needs a medium; it travels fastest in solids, slower in liquids and slowest in gases, and cannot travel in a vacuum.
Acids react with metals to release hydrogen gas and neutralise bases to form salt and water.
Elements are pure substances of one atom type; compounds are chemically combined; mixtures can be separated by physical means.
Photosynthesis converts light energy to chemical energy in glucose; respiration reverses it, releasing energy in cells.
Human body: the heart has four chambers; blood is pumped from the left ventricle to the body through the aorta.
Vaccines stimulate the immune system to produce antibodies, giving immunity without causing the full disease.
Reflection follows the law that angle of incidence equals angle of reflection; refraction bends light when it changes medium.
SI units: metre (length), kilogram (mass), second (time), ampere (current), kelvin (temperature), mole (amount), candela (luminous intensity).