IOE Entrance Nepal key terms

A physical quantity fully described by a magnitude alone, with no direction needed. Mass, speed, time, and temperature are examples, unlike vectors which also require a direction.

A physical quantity possessing both magnitude and direction, such as displacement, velocity, or force. Vectors add by geometric or component methods rather than simple arithmetic.

The single vector that produces the same effect as two or more vectors acting together. It is found by the parallelogram or triangle law of vector addition.

A body's resistance to change in its rotational motion, depending on mass and how that mass is distributed about the axis. It plays the role in rotation that mass plays in straight-line motion.

The turning effect of a force about a point or axis, equal to force multiplied by the perpendicular distance from the axis. It changes angular momentum and is measured in newton metres.

A measure of rotational motion equal to moment of inertia times angular velocity. It stays constant when no external torque acts, which explains why a spinning skater speeds up when pulling in their arms.

Oscillation in which the restoring force is directly proportional to displacement from equilibrium and directed opposite to it. Its displacement follows a sine or cosine curve with constant period regardless of amplitude.

The large-amplitude vibration that occurs when a system is driven at a frequency matching its own natural frequency. It underlies tuning circuits, musical instruments, and the collapse of bridges under rhythmic loading.

A disturbance that transfers energy through a medium or space without transporting matter. Waves are described by wavelength, frequency, amplitude, and speed, related by the wave equation.

The ratio of the speed of light in vacuum to its speed in a given medium. It determines how much a light ray bends at a boundary and governs total internal reflection.

The angle of incidence beyond which light travelling from a denser to a rarer medium is totally internally reflected instead of refracted. Its sine equals the reciprocal of the refractive index.

The time required for half the nuclei in a radioactive sample to decay. It is constant for a given isotope and allows dating of materials and calculation of remaining activity.

The spontaneous emission of alpha particles, beta particles, or gamma rays from unstable atomic nuclei as they transform into more stable configurations. It is a random process measured in becquerels.

The amount of substance containing exactly the Avogadro number of elementary particles, about 6.022 times ten to the twenty-third. It links mass in grams to numbers of atoms or molecules.

The concentration of a solution expressed as moles of solute per litre of solution. It changes slightly with temperature because solution volume expands, unlike molality.

Concentration expressed as gram equivalents of solute per litre of solution. It depends on the reaction involved, since one mole of an acid may supply more than one equivalent of hydrogen ions.

The simplest whole-number ratio of atoms of each element in a compound. It is derived from percentage composition and may differ from the actual molecular formula.

The calculation of quantities of reactants and products in a balanced chemical equation using mole ratios. It allows prediction of yields and identification of the limiting reactant.

A process in which a substance loses electrons, increases its oxidation number, or gains oxygen. It always occurs together with reduction in a redox reaction.

A process in which a substance gains electrons, decreases its oxidation number, or loses oxygen. The oxidizing agent is the species that is itself reduced.

The potential difference developed between an electrode and its surrounding solution, measured relative to the standard hydrogen electrode. Values predict which species is oxidised or reduced in a cell.

When a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, it shifts in the direction that opposes the change. It predicts how yields respond to altered conditions.

The ratio of product concentrations to reactant concentrations, each raised to its stoichiometric coefficient, at equilibrium. Its value depends only on temperature for a given reaction.

The mixing of atomic orbitals of similar energy to form new equivalent orbitals that explain observed molecular geometry and bond angles, such as the tetrahedral arrangement in methane.

One of two or more compounds sharing the same molecular formula but differing in arrangement of atoms, giving different structures or properties. Types include chain, position, and functional group isomers.

The tendency of an atom in a molecule to attract shared electrons toward itself. Differences in electronegativity between bonded atoms determine bond polarity and intermolecular forces.

A relatively strong attraction between a hydrogen atom bonded to nitrogen, oxygen, or fluorine and a lone pair on a nearby electronegative atom. It raises boiling points and shapes proteins and DNA.

The value a function approaches as its input approaches a specified point, whether or not the function equals that value there. Limits define continuity, derivatives, and integrals.

The instantaneous rate at which a function changes with respect to its variable, equal to the limit of a difference quotient. Geometrically it gives the slope of the tangent line.

The limit of a sum of areas of thin rectangles under a curve, representing accumulated change or area. Definite integrals are evaluated using antiderivatives via the fundamental theorem of calculus.

A property of a function that has no breaks, jumps, or holes at a point: the limit exists, the function is defined there, and the two are equal. Differentiability requires continuity but not the reverse.

A single number computed from a square matrix that indicates whether the matrix is invertible and scales areas or volumes under the associated transformation. It equals zero for singular matrices.

A rectangular array of numbers arranged in rows and columns, used to represent systems of linear equations and transformations. Matrices can be added, multiplied, and inverted under stated conditions.

An arrangement of items in which order matters, counted by factorials or by n factorial divided by the factorial of the unused items. It contrasts with combination, where order is irrelevant.

A selection of items from a group in which the order of selection does not matter. The count equals n factorial divided by the product of r factorial and the factorial of n minus r.

A number between zero and one expressing how likely an event is, calculated as favourable outcomes divided by total equally likely outcomes. It forms the basis of distributions and statistical inference.

A number of the form a plus bi, where a and b are real and i squared equals minus one. Complex numbers have modulus and argument and are represented as points in the Argand plane.

A curve obtained by intersecting a cone with a plane: circle, ellipse, parabola, or hyperbola. Each has a standard equation with eccentricity determining its shape.

A word having a meaning opposite to that of another word, such as hot and cold. Antonym questions test vocabulary range and precision of word meaning.

A word that has the same or nearly the same meaning as another word in a given context, such as begin and commence. Choosing correct synonyms requires attention to register and nuance.

A fixed expression whose meaning cannot be worked out from the individual words, such as to let the cat out of the bag. Idioms must be learned as whole units.

A verb combined with an adverb or preposition that together carry a meaning different from the verb alone, such as give up or look after. Particle choice often changes meaning entirely.

The grammatical rule that a verb must match its subject in number and person, so a singular subject takes a singular verb. Intervening phrases and collective nouns often cause errors.

The grammatical category that locates an action or state in time, such as present, past, or future, and marks whether it is continuous or completed. Correct sequence of tenses governs reported speech.

The force or demand placed on a structure or machine that it must safely support or carry. Loads may be dead, live, wind, or seismic, and determine member sizing.

Internal force per unit cross-sectional area within a material, measured in pascals. It may be tensile, compressive, or shear, and produces strain in the material.

The fractional change in length or shape of a material resulting from applied stress. It is dimensionless, and the ratio of stress to strain within the elastic range gives Young's modulus.

The ratio of the failure strength of a material or structure to the working stress it is expected to carry. It accounts for uncertainty in loads, materials, and analysis.

A graph plotting stress against strain for a material under increasing load. It reveals the elastic limit, yield point, ultimate strength, and ductility, guiding material selection.

For steady, incompressible, frictionless flow, an increase in fluid speed is accompanied by a decrease in pressure or potential energy. It explains lift and carburettor action.

A fluid's internal resistance to flow, arising from friction between adjacent layers moving at different speeds. It falls with rising temperature in liquids but rises in gases.

A material property describing how readily heat flows through it by conduction, measured in watts per metre per kelvin. Metals are high; insulators such as air are low.

The amount of heat energy required to raise the temperature of a body by one kelvin. Specific heat capacity is the same quantity per unit mass of material.