Gifu Entrance Science key terms

The rate at which an object's position changes in a stated direction, expressed as displacement divided by elapsed time. Unlike speed, it includes direction, so a change of direction changes velocity even if speed stays constant.

The rate at which velocity changes with time, including speeding up, slowing down, or changing direction. For motion in a straight line under constant force it is constant, and its SI unit is metres per second squared.

The net force on an object equals its mass multiplied by its acceleration (F = ma). The acceleration points in the same direction as the net force, and doubling the force doubles the acceleration for a fixed mass.

A measure of motion equal to mass times velocity (p = mv). It is a vector, so opposite directions cancel, and in a closed system the total momentum before and after a collision stays the same.

In a system with no external net force, the total momentum stays constant through any interaction. This lets you predict velocities after collisions and explosions by setting total momentum before equal to total momentum after.

The energy an object possesses because of its motion, equal to one half of mass times velocity squared (½mv²). Because velocity is squared, doubling speed quadruples kinetic energy for the same mass.

Energy cannot be created or destroyed, only transferred between forms or between objects. In mechanics, gravitational potential energy lost by a falling body appears as kinetic energy if friction and air resistance are negligible.

The distance between two consecutive corresponding points on a wave, such as crest to crest or compression to compression. It is usually represented by the Greek letter lambda and is measured in metres.

The number of complete wave cycles passing a fixed point each second, measured in hertz. Frequency is set by the source, and for a given wave speed a shorter wavelength corresponds to a higher frequency.

The distance a wave disturbance travels per unit time, equal to frequency multiplied by wavelength (v = fλ). For a given medium the speed is usually fixed, so changing frequency changes wavelength inversely.

The bending of a wave as it passes from one medium into another where its speed differs. The change in speed alters direction unless the wave strikes the boundary perpendicular to the surface.

For a conductor at constant temperature, current is directly proportional to potential difference, so V = IR. Resistance is measured in ohms and equals the voltage across a component divided by the current through it.

A measure of how strongly a component opposes the flow of electric current, measured in ohms. Longer, thinner wires have more resistance, and resistance generally rises with temperature in metal conductors.

In series, components form one path so the current is the same through each and voltages add. In parallel, components share branches so voltage is the same across each and branch currents add.

The rate at which a circuit component transfers electrical energy, equal to voltage multiplied by current (P = VI). It can also be written as I²R or V²/R and is measured in watts.

The energy needed to raise the temperature of one kilogram of a substance by one kelvin, measured in joules per kilogram per kelvin. Water's high value explains why it heats and cools slowly.

The energy absorbed or released when a substance changes state at constant temperature, such as melting or boiling. It breaks or forms bonds between particles rather than changing their average kinetic energy.

The state reached when two objects in contact have the same temperature, so no net heat flows between them. Heat always flows spontaneously from the hotter body to the cooler one until this state is reached.

The electrostatic attraction between oppositely charged ions formed when electrons transfer from a metal to a nonmetal. The resulting lattice is rigid with high melting points and conducts only when molten or dissolved.

A bond formed when two atoms share one or more pairs of electrons. It is typical between nonmetals and can be nonpolar or polar depending on how unequally the shared electrons are attracted.

A measure of how strongly an atom attracts the shared electrons in a bond. Large differences between bonded atoms produce ionic character, while small differences produce nonpolar covalent bonds.

The amount of substance containing 6.02 × 10²³ particles, known as Avogadro's number. It links particle counts to measurable mass, since one mole of a substance has a mass in grams equal to its formula mass.

The reactant that is used up first in a chemical reaction, determining the maximum amount of product that can form. Other reactants are in excess and remain after the reaction stops.

A reversible reaction's state where forward and reverse rates are equal, so concentrations stay constant though reactions continue. Changing temperature, pressure, or concentration shifts the balance according to Le Chatelier's principle.

The minimum energy colliding particles need for a reaction to occur. A catalyst lowers it by providing an alternative pathway, increasing the fraction of successful collisions without being consumed.

The net movement of water across a partially permeable membrane from a region of higher water potential to lower water potential. It is passive and explains water uptake by plant roots and cell shape changes.

Cell division producing two genetically identical daughter cells with the same chromosome number as the parent. It underlies growth, repair, and asexual reproduction, and is preceded by chromosome replication.

A two-stage division producing four daughter cells, each with half the parent's chromosome number. Crossing over and independent assortment during meiosis create genetic variation in the gametes formed.

One of the alternative versions of a gene at a particular position on a chromosome. An organism inherits one allele from each parent, and dominant alleles mask recessive ones in heterozygotes.

A control mechanism in which a change from a set point triggers a response that reverses the change. It keeps conditions such as body temperature and blood glucose stable within narrow limits.

The process by which individuals with inherited traits better suited to their environment survive and reproduce more, so those traits become more common over generations. It requires variation and differential reproduction.

The theory that Earth's rigid outer shell is broken into plates that move over the mantle. Their interactions at boundaries cause earthquakes, volcanic activity, mountain building, and ocean trench formation.

Vibrations released by earthquakes that travel through Earth. P waves are longitudinal and pass through solids and liquids, while S waves are transverse and cannot pass through liquids, revealing the liquid outer core.

The force per unit area exerted by the weight of air above a point. It decreases with altitude and drives winds as air moves from high-pressure to low-pressure regions, deflected by Earth's rotation.

In an experiment, the group that does not receive the treatment and is otherwise treated identically. Comparing it with the experimental group isolates the effect of the variable being tested.

The factor deliberately changed by the experimenter between trials. All other conditions must be kept constant so that any change in the dependent variable can be attributed to it.

Correlation means two variables change together, while causation means one actually produces the other. A correlation may arise from coincidence or a hidden third factor, so it alone cannot establish cause.