Kagoshima Entrance Science flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Newton's second law

The net force on an object equals its mass multiplied by its acceleration (F = ma). Doubling the net force doubles acceleration; doubling the mass halves acceleration for the same force.

Terminal velocity

The constant speed reached by a falling object when the upward drag force equals its weight, so the net force is zero and acceleration stops.

Kinetic energy formula

Kinetic energy equals one half of the mass times the speed squared (KE = ½mv²). Because speed is squared, doubling speed increases kinetic energy four times.

Conservation of energy

Energy cannot be created or destroyed, only transferred between stores or transformed from one form to another. The total energy in a closed system stays constant.

Law of reflection

The angle of incidence equals the angle of reflection. Both angles are measured between the ray and the normal, an imaginary line perpendicular to the mirror surface at the point of incidence.

Wave equation

Wave speed equals frequency multiplied by wavelength (v = fλ). Frequency is measured in hertz, wavelength in metres, and speed in metres per second.

Exothermic reaction

A chemical reaction that transfers energy to the surroundings, usually detected by a rise in temperature. Combustion and neutralisation are common examples.

Conservation of mass

In a chemical reaction in a closed system, the total mass of the reactants equals the total mass of the products, because atoms are rearranged but never created or destroyed.

Balancing equations rule

Coefficients in front of formulas are adjusted so each element has the same atom count on both sides. Subscripts inside a formula must never be changed.

Mole concept

One mole contains 6.02 × 10²³ particles. The number of moles equals mass divided by relative formula mass, linking masses to equation ratios.

Neutralisation ionic equation

The reaction of hydrogen ions from an acid with hydroxide ions from a base produces water: H⁺ + OH⁻ → H₂O. The remaining ions form the dissolved salt.

pH scale

A scale from 0 to 14 measuring hydrogen ion concentration. Values below 7 are acidic, 7 is neutral, and above 7 is alkaline; each unit is a tenfold change.

Mitosis versus meiosis

Mitosis produces two genetically identical diploid cells for growth and repair. Meiosis produces four genetically varied haploid gametes, halving the chromosome number before fertilisation.

Osmosis

The diffusion of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration, requiring no added energy.

Dominant and recessive alleles

A dominant allele is expressed even when only one copy is present. A recessive allele is expressed only when both copies are recessive, so recessive traits can skip generations.

Genotype and phenotype

Genotype is the combination of alleles an organism carries, such as Aa or aa. Phenotype is the observable characteristic produced by that genotype and the environment.

Energy transfer in food chains

Only about ten percent of energy passes from one trophic level to the next. The rest is lost as heat, used in movement, or egested, limiting chain length.

Decomposers

Organisms such as bacteria and fungi that break down dead organisms and waste. They release nutrients back into the soil for producers to absorb.

Principle of superposition

In undisturbed sedimentary strata, each layer is younger than the layer below it and older than the layer above it, giving relative ages without radiometric dating.

Cross-cutting relationships

A fault, crack, or igneous intrusion is younger than the rock it cuts through. This rule lets geologists order events even when strata are tilted.

Air pressure and altitude

Air pressure falls as altitude increases because fewer air molecules lie above the observer. Pressure is also lower in warm, rising air than in cold, sinking air.

Cold front weather

A cold air mass pushes under warm air, forcing rapid uplift. This produces brief heavy rain, often thunderstorms, followed by clear skies and a sharp temperature drop.

Cause of the seasons

Earth's axis is tilted about 23.4 degrees, so each hemisphere receives sunlight at a different angle and for a different duration as Earth orbits the Sun.

Spring and neap tides

Spring tides are large tides at new and full moon when solar and lunar pulls align. Neap tides are small tides at quarter moons when the pulls act at right angles.

Independent variable

The factor deliberately changed by the experimenter in an investigation. It is plotted on the horizontal axis, while the dependent variable is measured and plotted vertically.

Control variables

Factors kept constant throughout an experiment so that any change in the dependent variable can be attributed to the independent variable rather than to other influences.

Speed versus velocity

Speed is a scalar giving distance travelled per unit time. Velocity is a vector, so it includes direction; a change in direction is a change in velocity.

Power and efficiency

Power is energy transferred per second, measured in watts. Efficiency is useful output energy divided by total input energy, expressed as a percentage.

Refraction of light

Light changes speed when crossing between media of different optical density, bending toward the normal in a denser medium and away from it in a less dense one.

Catalyst

A substance that increases the rate of a reaction by providing an alternative pathway with lower activation energy, without being used up or changing the final products.

Ionic bonding

A metal atom transfers electrons to a non-metal atom, forming a positively charged cation and a negatively charged anion. Electrostatic attraction holds the ions in a lattice.

Human gametes and fertilisation

Sperm and egg are haploid gametes with 23 chromosomes each. Their fusion at fertilisation produces a diploid zygote with 46 chromosomes, restoring the full set.