MBBS/BDS Admission key terms

The curved path followed by an object thrown into the air, where only gravity acts after launch. Horizontal and vertical motions are treated separately, giving a parabolic trajectory.

The constant rate at which freely falling bodies gain speed near Earth's surface, about 9.8 metres per second squared, directed downward toward Earth's centre.

Motion of a body under gravity alone, with air resistance ignored. All bodies in free fall near Earth accelerate downward at the same rate regardless of mass.

A single vector that produces the same overall effect as two or more vectors combined. It is found by head-to-tail addition or by resolving components along perpendicular axes.

The turning effect of a force about a pivot, calculated as force multiplied by the perpendicular distance from the pivot to the line of action of the force.

A measure of how strongly a body resists change in its rotational motion. It depends on mass and on how that mass is distributed about the axis of rotation.

The quantity of rotational motion of a body, equal to moment of inertia times angular velocity. It stays constant when no external torque acts on the system.

Oscillation in which the restoring force is directly proportional to displacement from equilibrium and directed opposite to it, giving a sinusoidal displacement-time graph.

A large increase in oscillation amplitude that occurs when a system is driven at a frequency matching its own natural frequency.

The apparent change in frequency of a wave when the source, the observer, or both move relative to the medium. Approach raises observed frequency; recession lowers it.

The distance a wave crest travels per unit time, equal to frequency multiplied by wavelength. It is set by the medium, not by the source alone.

Complete reflection of light back into a denser medium when it strikes the boundary at an angle greater than the critical angle, so no refracted ray emerges.

The ratio of the speed of light in vacuum to its speed in a given medium. It measures how strongly the medium bends light entering it.

The angle of incidence in the denser medium for which the refracted ray grazes along the boundary. Beyond it, total internal reflection occurs.

Emission of electrons from a metal surface when light of sufficiently high frequency strikes it. It shows that light delivers energy in discrete packets called photons.

The minimum energy needed to remove an electron from the surface of a particular metal. Light below the matching threshold frequency cannot cause emission.

The time taken for half the nuclei in a radioactive sample to decay, or for half the atoms of a reactant to be consumed in a first-order reaction.

The idea that one mole contains Avogadro's number of particles, about 6.02 times ten to the twenty-three, and has a mass in grams equal to the relative molecular mass.

The concentration of a solution expressed as moles of solute dissolved per litre of solution. It changes slightly with temperature because volume expands or contracts.

Concentration expressed as gram equivalents of solute per litre of solution. For acids and bases it accounts for the number of replaceable hydrogen or hydroxide ions.

The reactant that is completely used up first in a chemical reaction, thereby fixing the maximum amount of product that can form.

The simplest whole-number ratio of atoms of each element present in a compound, obtained from percentage composition data.

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

The power to which the concentration of a reactant is raised in the experimentally determined rate law. It is not necessarily related to the balanced equation coefficients.

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

The ratio of product concentrations to reactant concentrations, each raised to its stoichiometric power, at equilibrium. Its value depends on temperature.

The tendency of an atom in a bond to attract the shared electron pair toward itself. Large differences between bonded atoms produce polar bonds.

The mixing of atomic orbitals of similar energy to form new equivalent orbitals that give the observed geometry of a molecule, such as tetrahedral or trigonal planar.

One of two or more equivalent electron-dot representations of a molecule in which electrons are delocalised; the real structure is a blend of them all.

A strong attraction between a hydrogen atom bonded to an electronegative atom and a lone pair on a nearby electronegative atom, raising boiling points and shaping biomolecules.

The net movement of water across a partially permeable membrane from a region of higher water potential to one of lower water potential.

The tendency of water to move from one region to another, measured in pressure units. Pure water at atmospheric pressure has the highest possible value, zero.

Shrinkage of a plant cell's protoplast away from the cell wall when the cell loses water by osmosis in a strongly hypertonic solution.

Loss of a protein's three-dimensional shape and function caused by heat, extreme pH, or chemicals, which break bonds holding the folded structure together.

A biological catalyst, usually a protein, that speeds a specific reaction by lowering its activation energy and binds substrates at an active site.

A non-protein substance, such as a metal ion or coenzyme, required by an enzyme to become catalytically active.

The process in which a DNA strand is used as a template to build a complementary messenger RNA molecule, catalysed by RNA polymerase.

The process in which ribosomes read messenger RNA codons and assemble the corresponding sequence of amino acids into a polypeptide chain.

A sequence of three consecutive nucleotides in messenger RNA that specifies one amino acid or signals the start or end of translation.