RRB JE Mechanical key terms

The smallest positive number that is a multiple of each of two or more given integers. It equals the product of the numbers divided by their highest common factor, and is used when adding fractions or aligning repeating events.

The largest positive integer that divides two or more given numbers without leaving a remainder. Also called the greatest common divisor; it is used to simplify fractions and to split quantities into equal maximum-sized groups.

Interest computed on the original principal plus all interest already earned, so the amount grows faster than under simple interest. For principal P, rate r and n compounding periods per year, A = P(1 + r/n)^(nt).

The branch of geometry dealing with measuring lengths, areas, surface areas and volumes of plane and solid figures such as triangles, circles, cylinders, cones and spheres.

An equation of the form ax² + bx + c = 0 where a is not zero. Its two roots come from factorisation or the quadratic formula, and the discriminant b² − 4ac shows whether the roots are real.

A form of deductive reasoning in which two or more premises assumed true lead to a conclusion. Candidates decide whether that conclusion necessarily follows, or is only possible, or cannot follow at all.

A reasoning topic in which letters, digits or words are converted into a code by a fixed rule, such as shifting alphabet positions or reversing order, and the candidate must decrypt a new word using the same rule.

Reasoning problems that describe family links through words or symbols and ask how two people are related. Candidates draw a family tree, marking gender and generation, to avoid confusing in-laws with blood relatives.

A sequence of numbers built on a rule such as a constant difference, a constant ratio, squares, cubes or alternating operations. The task is to identify the rule and supply the missing or wrong term.

Basic freedoms guaranteed by Part III of the Indian Constitution, covering equality, speech, life and liberty, and constitutional remedies. They are enforceable in courts through writs, though reasonable restrictions apply.

India's indirect tax on the supply of goods and services, introduced in 2017, which replaced many central and state levies. It is destination-based and applied at slab rates including 5, 12, 18 and 28 percent.

The rate at which the Reserve Bank of India lends short-term funds to commercial banks against government securities. Raising it usually cools inflation by making credit more expensive.

The acceleration of a body is directly proportional to the net force acting on it and inversely proportional to its mass, expressed as F = ma, with force in newtons when mass is in kilograms.

The process by which green plants use sunlight, water and carbon dioxide to make glucose and release oxygen. Chlorophyll inside chloroplasts absorbs the light energy that drives the reaction.

A logarithmic scale from 0 to 14 measuring hydrogen ion concentration: below 7 is acidic, 7 is neutral and above 7 is basic. Each unit step means a tenfold change in concentration.

At constant temperature, the current through a conductor is directly proportional to the potential difference across it, giving V = IR, where R is the resistance measured in ohms.

The heat absorbed or released when a substance changes state without any change in temperature, as in melting or boiling. For water, the latent heat of fusion is about 334 joules per gram.

When a system at equilibrium is disturbed by a change in concentration, pressure or temperature, the equilibrium shifts in the direction that partly opposes the change and restores a new balance.

A process in which an atom, ion or molecule loses electrons, shown by an increase in oxidation number. In a redox reaction it is always accompanied by the reduction of another species.

PV = nRT relates the pressure, volume, amount and absolute temperature of an ideal gas, where R is the universal gas constant. It combines Boyle's, Charles's and Avogadro's laws into one expression.

The ratio of the speed of light in vacuum to its speed in a given medium, showing how strongly that medium bends light. Water is about 1.33 and ordinary glass about 1.5.

System software that manages hardware, memory, files and running processes and provides services to application programs. Common examples are Windows, Linux, macOS and Android.

A unique numeric label assigned to a device on a network so that data packets can be routed to it, such as 192.168.1.1 under IPv4 or a longer hexadecimal form under IPv6.

A program that translates an entire source file written in a high-level language into machine code before the program runs, listing all syntax errors together rather than line by line.

Hardware or software that filters incoming and outgoing network traffic according to configured rules, blocking unauthorised access while allowing approved connections to pass through.

Volatile primary memory that holds the programs and data currently in use and allows fast reading and writing. Its contents are lost when the computer is switched off.

Warming of Earth's surface as gases such as carbon dioxide, methane and water vapour trap outgoing infrared radiation. It keeps the planet habitable but intensifies as extra emissions accumulate.

The amount of dissolved oxygen consumed by microorganisms while breaking down organic matter in a water sample, usually measured over five days at 20 °C. It is a key indicator of organic pollution.

Excess nutrients such as nitrates and phosphates entering a water body trigger heavy algal growth; when the algae decay, dissolved oxygen falls and fish and other aquatic life may die.

A statutory process that identifies and predicts the environmental effects of a proposed project before it is approved, and prescribes mitigation measures along with public consultation.

The internal resisting force per unit area developed within a material when an external load tends to deform it, measured in pascals or newtons per square millimetre.

Within the elastic limit, the stress produced in a material is directly proportional to the strain, and the constant of proportionality is the modulus of elasticity, commonly Young's modulus.

For steady, incompressible, frictionless flow along a streamline, the sum of pressure energy, kinetic energy and potential energy per unit weight of fluid remains constant.

A dimensionless ratio of inertial forces to viscous forces in a flow, used to classify it as laminar or turbulent. In pipes, values below roughly 2000 indicate laminar flow.

The ratio of a material's ultimate or yield strength to the working stress actually applied, showing how much reserve capacity a design keeps beyond the expected service load.

The ratio of the number of teeth on the driven gear to that on the driving gear, which fixes how speed and torque change between the two shafts.