Yamaguchi Prefectural Public High School Entrance Examination - Science flashcards

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

Average speed

Total distance travelled divided by total time taken. A car covering 120 m in 8 s has an average speed of 15 m/s, regardless of any changes in speed during the trip.

Newton's second law

The net force on an object equals mass times acceleration (F = ma). Doubling the net force doubles acceleration, while doubling the mass halves it for the same force.

Action-reaction pair

Forces described by Newton's third law: equal in size, opposite in direction, acting on two different objects. Because they act on different bodies, they never cancel each other.

Terminal velocity

The constant speed reached by a falling object when air resistance equals its weight. Net force becomes zero, so acceleration stops and speed no longer increases.

Kinetic energy formula

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

Mechanical energy conservation

Without friction or air resistance, the sum of kinetic and potential energy stays constant. A ball dropped from height h reaches ½mv² = mgh at the ground.

Ohm's law

The voltage across a conductor equals current times resistance (V = IR). For a fixed resistor, doubling voltage doubles current, giving a straight-line graph.

Parallel circuit rule

In parallel branches the voltage across each branch is equal to the supply voltage, and the total current is the sum of the branch currents.

Electrical power

Power equals voltage times current (P = VI), also written I²R or V²/R. A 100 V device drawing 2 A uses 200 W of power.

Physical versus chemical change

A physical change alters state, shape, or size without forming a new substance. A chemical change produces new substances with different properties and is usually irreversible.

Density and floating

Density equals mass divided by volume. An object floats in a liquid when its density is less than the liquid's, so ice floats on water.

Neutralisation

The reaction of an acid with an alkali to produce a salt and water. The resulting solution is closer to neutral, as when hydrochloric acid reacts with sodium hydroxide.

Distillation

A separation method using different boiling points. Heating a solution evaporates the more volatile liquid, which is then condensed and collected in a separate container.

Balanced chemical equation

An equation in which the number of atoms of each element is equal on both sides. Coefficients are adjusted to achieve this because atoms are conserved in reactions.

Mole

The amount of substance containing 6.0 × 10²³ particles. One mole of any substance has a mass in grams equal to its formula mass.

Molar mass

The mass of one mole of a substance in grams per mole. It is found by summing the atomic masses in the formula, such as 18 g/mol for water.

Ion formation

An atom becomes an ion by gaining or losing electrons. The proton number is unchanged, so the element stays the same but its charge changes.

Food chain energy loss

Only about ten percent of energy passes to the next trophic level; the rest is lost as heat and in waste. This limits food chains to a few links.

Decomposers

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

Mutualism

A symbiotic relationship in which both species benefit. For example, bees gain nectar from flowers while transferring pollen between plants.

Natural selection

Organisms with inherited traits suited to their environment survive and leave more offspring. Over generations, those favourable traits become more common in the population.

Small intestine villi

Finger-like projections lining the small intestine. They greatly increase surface area so digested nutrients are absorbed efficiently into blood and lymph.

Double circulation

Blood passes through the heart twice per circuit: pulmonary flow to the lungs and systemic flow to the body. This keeps oxygenated and deoxygenated blood separate.

Reflex arc

The pathway of an involuntary response: receptor, sensory neuron, spinal cord, motor neuron, effector. It bypasses conscious brain decisions to react quickly.

Insulin

A hormone from the pancreas that lowers blood glucose by promoting uptake into cells and storage as glycogen in the liver.

Cause of the seasons

Earth's 23.4° axial tilt changes the angle and duration of sunlight through the year. The hemisphere tilted toward the Sun receives more intense light and has summer.

P waves and S waves

Seismic body waves. P waves are fastest and travel through solids and liquids; S waves travel only through solids, revealing Earth's liquid outer core.

Igneous rock

Rock formed when magma or lava cools and solidifies. Slow cooling underground gives large crystals, while rapid cooling at the surface gives fine crystals.

Air pressure and weather

Air pressure decreases with altitude. High pressure brings descending air and clear weather; low pressure brings rising air, clouds, and precipitation.

Dew point

The temperature at which air becomes saturated and water vapour condenses. Cooling air below its dew point produces dew, fog, or cloud droplets.

Sea breeze

A daytime wind blowing from sea to land. Land heats faster than water, so air over land rises and cooler sea air flows in to replace it.

Control variables

Factors kept constant in an experiment so that only the independent variable affects the result. They allow a fair comparison between experimental groups.