Kochi Entrance Science key terms

The straight-line distance and direction from an object's starting point to its current position. It is a vector quantity, so reversing direction reduces displacement even while distance travelled keeps growing.

The rate of change of displacement with time, including direction. Average velocity equals total displacement divided by total time, while instantaneous velocity is the value at one moment.

The rate at which velocity changes with time, whether in magnitude, direction, or both. A body moving in a circle at constant speed still accelerates because its direction changes.

The net force on a body equals its mass multiplied by its acceleration, written F = ma. It links force to the change in motion rather than to motion itself.

The product of a body's mass and its velocity, a vector pointing along the motion. In a closed system with no external net force, total momentum stays constant through collisions and explosions.

Energy cannot be created or destroyed, only transferred between stores or transformed between forms. In mechanics, the sum of kinetic and potential energy stays constant when only conservative forces act.

The energy transferred when a force moves an object along its line of action, calculated as force times displacement in the force direction. A force perpendicular to motion does no work.

The rate at which work is done or energy is transferred, measured in watts, where one watt equals one joule per second. It tells how quickly energy moves, not how much is moved.

A quantity with both magnitude and direction, such as force, velocity, or electric field. Vectors add by the parallelogram or triangle rule, not by simple arithmetic of their sizes.

A quantity described fully by magnitude alone, with no direction, such as mass, time, temperature, or speed. Scalars add arithmetically, unlike vectors.

The curved path of an object moving under gravity alone after being launched, with constant horizontal velocity and constant vertical acceleration. The two perpendicular components can be analysed independently.

The distance between two consecutive points in phase on a wave, such as crest to crest. It equals wave speed divided by frequency for any periodic wave.

The number of complete oscillations or wave cycles passing a point each second, measured in hertz. It is set by the source and does not change when a wave crosses into a new medium.

The time taken for one complete oscillation or wave cycle, measured in seconds. It is the reciprocal of frequency, so a 5 Hz wave has a period of 0.2 s.

The distance a wave crest travels per second, given by speed equals frequency times wavelength. It depends on the medium, so a wave changes speed and wavelength but not frequency when entering a new material.

The change in direction of a wave as it passes between media of different wave speeds. The frequency stays fixed while wavelength and speed change, with bending towards the normal in a slower medium.

The spreading of waves after passing an obstacle or through a gap, most noticeable when the gap is comparable in size to the wavelength. Longer wavelengths diffract more strongly.

The principle that when two or more waves meet, the resultant displacement at each point is the sum of the individual displacements. It explains interference, standing waves, and beats.

The reinforcement or cancellation that occurs when waves overlap. Constructive interference gives a larger amplitude when crests align, while destructive interference gives a smaller amplitude when a crest meets a trough.

A pattern formed by two identical waves travelling in opposite directions, producing fixed nodes and antinodes. It stores energy without transporting it along the medium.

A large amplitude response that occurs when a system is driven at one of its natural frequencies. Energy transfer is most efficient at resonance, which can strengthen signals or damage structures.

The rate of flow of electric charge past a point, measured in amperes, where one ampere is one coulomb per second. Conventional current is taken as the direction of positive charge flow.

The work done per unit charge in moving charge between two points in a circuit, measured in volts. It is the energy transferred from the source to each coulomb of charge.

A measure of how strongly a component opposes current, equal to potential difference divided by current and measured in ohms. It arises from collisions between charge carriers and the material's lattice.

The statement that current through a conductor is directly proportional to potential difference across it, provided temperature stays constant. Components obeying it have a straight-line current-voltage graph through the origin.

A circuit in which components are connected in a single loop, so the same current flows through each. Total resistance is the sum of the individual resistances and the supply voltage divides between them.

A circuit in which components are connected across the same two points, so each receives the full supply voltage. The total current is the sum of branch currents and total resistance is less than any single branch.

The generation of an electromotive force in a conductor when the magnetic flux through it changes, as when a magnet moves near a coil. The induced current opposes the change that produced it.

The amount of magnetic field passing through a given area, found by multiplying field strength by area for a perpendicular field. Its rate of change determines the size of an induced voltage.

The electrostatic attraction between oppositely charged ions formed when one atom transfers electrons to another. It typically arises between metals and non-metals and creates a giant lattice structure.

A bond formed when two atoms share one or more pairs of electrons, usually between non-metals. The shared pair is attracted to both nuclei, holding the atoms together.

A measure of how strongly an atom attracts the shared electron pair in a covalent bond. Large differences between bonded atoms make the bond polar or, if extreme, ionic.

The amount of substance containing 6.02 × 10^23 elementary particles, the Avogadro constant. It links the mass of a sample to the number of particles and to gas volumes.

The mass of one mole of a substance in grams per mole, numerically equal to its relative formula mass. It converts between mass in grams and amount in moles.

The reactant that is completely used up first in a chemical reaction, fixing the maximum amount of product formed. Other reactants remain in excess after the reaction stops.

The state of a reversible reaction in a closed system where forward and reverse rates are equal, so concentrations stay constant. Both reactions continue, but there is no net change.

When a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, the position of equilibrium shifts to oppose that change. It predicts the direction of shift, not the rate.

A substance that increases the rate of a reaction by providing an alternative pathway of lower activation energy, without being consumed. It speeds the approach to equilibrium but does not change its position.

Cell division producing two genetically identical daughter cells with the same chromosome number as the parent. It supports growth, repair, and asexual reproduction in body cells.

A reduction division producing four genetically varied gametes, each with half the parent's chromosome number. Crossing over and independent assortment during meiosis create genetic variation.

One of the alternative versions of a gene occupying the same position on homologous chromosomes. An organism's combination of alleles determines its genotype and can influence its phenotype.

The particular combination of alleles an organism carries for a gene or set of genes. It may be homozygous, with two identical alleles, or heterozygous, with two different alleles.

The observable characteristics of an organism resulting from its genotype interacting with the environment. Dominant alleles are expressed even when only one copy is present.

The net movement of water across a partially permeable membrane from a region of higher water potential to one of lower water potential. It requires no energy from the cell.

The net movement of particles from a region of higher concentration to lower concentration, driven by random motion. It is passive and continues until concentrations are equal.

The movement of substances across a membrane against their concentration gradient, using energy from ATP and carrier proteins. It allows cells to accumulate ions or nutrients at higher concentrations than outside.

A protein that catalyses a specific biochemical reaction by lowering its activation energy. Its activity depends on temperature and pH, and is lost if the active site is denatured.

The maintenance of a stable internal environment, such as constant body temperature and blood glucose, despite external change. It relies on negative feedback loops detecting and correcting deviations.

A control mechanism in which a detected deviation triggers a response that reduces that deviation, restoring the set point. It stabilises conditions such as temperature and blood sugar.

A function of the form f(x) = ax^2 + bx + c with a not equal to zero, whose graph is a parabola. Its turning point and roots can be found by completing the square or using the discriminant.

The expression b^2 − 4ac for a quadratic equation, revealing the number of real roots. A positive value gives two real roots, zero gives one repeated root, and a negative value gives none.

A rule that assigns exactly one output value to each input value in its domain. Its graph passes the vertical line test, and its inverse exists only if it is one-to-one.

The complete set of input values for which a function is defined. For a function containing a square root, the expression inside must be non-negative; for a fraction, the denominator cannot be zero.

The set of all output values a function actually produces from its domain. For a quadratic with a positive leading coefficient, the range is bounded below by the minimum value.

The instantaneous rate of change of a function with respect to its variable, equal to the gradient of the tangent to its graph. It is found as the limit of the gradient of a chord as the interval shrinks to zero.

The steepness of a line or curve, calculated as the change in the vertical coordinate divided by the change in the horizontal coordinate. For a curve it varies from point to point.

A point on a curve where the gradient is zero, so the tangent is horizontal. It may be a maximum, a minimum, or a point of inflection, distinguished using the second derivative.

The reverse process of differentiation, used to find a function from its gradient or to calculate the area under a curve. A definite integral evaluates this area between two limits.

A value of the variable that makes the equation true, shown graphically where the curve crosses the horizontal axis. Numerical methods can approximate roots when no exact solution exists.