KUUMAT Nepal key terms

The net force on a body equals its mass times its acceleration, so a larger mass or a larger force changes how quickly velocity changes. Written as F = ma for constant mass.

The product of a body's mass and its velocity, a vector quantity that measures how hard it is to stop the body. Its rate of change equals the net applied force.

In a system with no net external force, the total momentum before and after an interaction stays the same. Used to solve collision and explosion problems.

A collision in which both total momentum and total kinetic energy are conserved. Billiard-ball-like impacts approximate this ideal case.

A sketch showing a single body isolated with every external force drawn as an arrow from it. It helps convert a physical situation into force equations.

A contact force that opposes relative sliding between surfaces. Its limiting value depends on the normal force and the roughness of the surfaces.

The net work done on a body equals its change in kinetic energy. It links force and displacement directly to speed changes without tracking time.

The energy a body possesses because of its motion, equal to half its mass times the square of its speed. It is always non-negative.

Energy cannot be created or destroyed, only changed from one form to another. In mechanics, the sum of kinetic and potential energy stays constant when only conservative forces act.

Oscillation in which the restoring force is directly proportional to displacement and directed toward the equilibrium point. Its period is independent of amplitude.

The time taken for one complete cycle of a repeating motion, such as an oscillation or a wave. It is the reciprocal of frequency.

The ratio of the speed of light in vacuum to its speed in a medium. It determines how much a ray bends when entering the medium.

Complete reflection of light back into a denser medium when it strikes a boundary beyond the critical angle. It requires travel from denser to rarer medium.

For a conductor at constant temperature, current is directly proportional to potential difference across it. The constant of proportionality is resistance.

The opposition a component offers to current flow, measured in ohms. It equals the potential difference across the component divided by the current through it.

The amount of substance containing as many elementary entities as there are atoms in 12 grams of carbon-12. That count is Avogadro's number, about 6.022 x 10^23.

The number of particles in one mole of a substance, approximately 6.022 x 10^23 per mole. It bridges the microscopic count of particles and measurable macroscopic amounts.

The mass of one mole of a substance, expressed in grams per mole. Numerically it equals the relative molecular mass of the substance.

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

The reactant that is used up first in a chemical reaction and therefore caps the amount of product formed. Others remain in excess.

Loss of electrons by a species, which corresponds to an increase in its oxidation number. It is always accompanied by reduction of another species.

Gain of electrons by a species, corresponding to a decrease in its oxidation number. Reduction and oxidation always occur together in a redox reaction.

A bookkeeping value assigned to an atom in a compound, treating bonding electrons as belonging to the more electronegative atom. It tracks electron transfer in redox reactions.

When a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, it shifts in the direction that partially opposes the change.

A state in a reversible reaction where forward and reverse rates are equal, so concentrations of reactants and products remain constant over time.

A logarithmic scale of hydrogen-ion concentration, defined as the negative logarithm of that concentration. Values below 7 are acidic and above 7 are basic at room temperature.

A solution that resists large changes in pH when small amounts of acid or base are added. It usually contains a weak acid with its conjugate base.

One of two or more compounds with the same molecular formula but different arrangements of atoms or different spatial orientation. They can differ greatly in properties.

A specific cluster of atoms within a molecule that gives it characteristic chemical behaviour, such as a hydroxyl, carboxyl, or amino group.

The net movement of water across a selectively permeable membrane from a region of higher water potential to one of lower water potential. It does not require energy input.

The tendency of water to move from one place to another, expressed in pressure units. Pure water at atmospheric pressure has a value of zero.

Shrinking of the protoplast away from the cell wall when a plant cell loses water in a strongly hypertonic solution. It demonstrates the osmotic behaviour of plant cells.

The process by which green plants use light energy to convert carbon dioxide and water into glucose and oxygen. It occurs mainly in chloroplasts.

The green pigment in chloroplasts that absorbs light energy for photosynthesis. It absorbs red and blue wavelengths most strongly and reflects green.

The two alleles of a gene separate during gamete formation so that each gamete carries only one of them. Their reunion at fertilization restores the pair.

The genetic makeup of an organism at a particular locus, described by the alleles it carries. It interacts with the environment to produce the observable phenotype.

The observable characteristics of an organism resulting from its genotype and its environment. Examples include flower colour, blood group, and height.

The system of naming species with two Latin terms, a capitalized genus name followed by a lowercase species epithet. Both are conventionally italicized.

The branch of biology concerned with identifying, naming, and classifying organisms into hierarchical groups. Its ranks run from kingdom down to species.

An arrangement of items in which order matters. The number of permutations of n distinct items taken r at a time is n! divided by (n minus r) factorial.

A selection of items in which order does not matter. The number of ways to choose r items from n is the corresponding permutation count divided by r factorial.

The instantaneous rate at which a function changes with respect to its variable, interpreted as the slope of the tangent to its graph at a point.

The value a function approaches as its input approaches a particular point, even if the function is not defined at that point itself. It underlies continuity and differentiation.

The sum of a set of values divided by the number of values. It is the most common measure of central tendency.

A measure of how spread out values are around their mean, found by taking the square root of the average squared deviation.

A number between zero and one expressing how likely an event is, calculated as favourable outcomes divided by total equally likely outcomes.