Fukushima 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 times its acceleration, F = ma. Acceleration points in the direction of the net force and is inversely proportional to mass.

Conservation of momentum

In a system with no external net force, total momentum before an interaction equals total momentum after. This holds for both elastic and inelastic collisions, unlike kinetic energy.

Ohm's law

For an ohmic conductor at constant temperature, voltage equals current times resistance, V = IR. Resistance is the ratio V/I and is measured in ohms.

Parallel resistors

Across parallel branches the voltage is identical, and total current is the sum of branch currents. The reciprocal of total resistance equals the sum of the reciprocals of individual resistances.

Wave speed equation

Wave speed equals frequency times wavelength, v = fλ. Frequency is set by the source and stays constant when a wave enters a new medium, so wavelength changes with speed.

Snell's law

For light crossing an interface, n₁ sin θ₁ = n₂ sin θ₂, where n is refractive index and angles are measured from the normal. Entering a denser medium bends light toward the normal.

Kinetic energy

Kinetic energy is one-half mass times speed squared, KE = ½mv². Doubling speed quadruples kinetic energy, which is why stopping distance grows with the square of speed.

Work-energy theorem

The net work done on an object equals its change in kinetic energy. Work is force times displacement times the cosine of the angle between them.

Mole and molar mass

The number of moles equals mass divided by molar mass, n = m/M. One mole of any substance contains about 6.02 × 10²³ particles.

Molarity

Molarity is moles of solute per liter of solution. When diluting, solute moles stay constant, so initial molarity times initial volume equals final molarity times final volume.

Ideal gas law

PV = nRT relates pressure, volume, moles, and absolute temperature, with R about 8.31 J/(mol·K). Temperature must be in kelvin, not degrees Celsius.

pH scale

pH equals the negative logarithm of hydrogen ion concentration. Each one-unit drop in pH means a tenfold increase in hydrogen ion concentration, so pH 3 is ten times more acidic than pH 4.

Oxidation and reduction

Oxidation is loss of electrons and a rise in oxidation number; reduction is gain of electrons and a fall. The two always occur together in a redox reaction.

Le Chatelier's principle

When a system at equilibrium is disturbed, it shifts to oppose the change. Adding reactant shifts forward; raising temperature favors the endothermic direction.

Limiting reactant

The reactant that is used up first limits how much product can form. Compare the available moles of each reactant with the mole ratio from the balanced equation.

Strong versus weak acids

Strong acids ionize essentially completely in water, while weak acids ionize only partially. At equal concentration, the strong acid gives lower pH and higher conductivity.

Balancing chemical equations

A balanced equation has equal numbers of each type of atom on both sides. Coefficients are adjusted, never subscripts, because changing subscripts would change the substance.

Cell theory

All living organisms are composed of one or more cells, the cell is the basic unit of structure and function, and new cells arise from existing cells by division.

Mitochondria function

Mitochondria carry out aerobic respiration, using oxygen to convert glucose into ATP, carbon dioxide, and water. Cells with high energy demand, such as muscle cells, contain many mitochondria.

Transcription and translation

Transcription copies a DNA template into messenger RNA in the nucleus. Translation at ribosomes reads mRNA codons and assembles the corresponding amino acid sequence into a protein.

Monohybrid cross ratio

Crossing two heterozygotes for one gene gives a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio. The recessive phenotype appears only in homozygous recessive offspring.

Enzyme activity

Enzymes lower activation energy and are unchanged by the reaction. Activity is highest near an optimum temperature and pH and drops sharply when the enzyme denatures.

Photosynthesis equation

Six carbon dioxide molecules plus six water molecules, using light energy, produce one glucose molecule and six oxygen molecules. Light reactions occur in thylakoid membranes; the Calvin cycle occurs in the stroma.

Diffusion versus active transport

Diffusion moves particles down a concentration gradient without energy input. Active transport moves substances against a gradient and requires ATP, often through carrier proteins.

Meiosis outcome

Meiosis halves chromosome number. Homologous chromosomes separate in meiosis I and sister chromatids in meiosis II, producing four genetically varied haploid cells.

Earth's layered interior

Earth consists of crust, mantle, and core. The liquid outer core generates the magnetic field through dynamo action, while the inner core is solid despite high temperature.

Plate boundary types

Divergent boundaries create new crust at mid-ocean ridges. Convergent boundaries produce subduction, volcanoes, and mountains. Transform boundaries slide horizontally and generate earthquakes.

Seismic wave types

P waves are longitudinal and travel through solids and liquids. S waves are transverse, travel only through solids, and arrive later, so their absence reveals a liquid outer core.

Kepler's third law

The square of an orbital period is proportional to the cube of the semimajor axis. With period in years and distance in astronomical units, T² equals a³.

Cause of seasons

Seasons result from Earth's 23.4-degree axial tilt, which changes the angle and duration of sunlight through the year. Distance from the Sun is not the main cause.

Moon phases

Phases arise from the changing angle between Earth, Moon, and Sun as the Moon orbits. The Moon does not emit its own light; we see reflected sunlight.

Three rock types

Igneous rock forms from cooling magma or lava. Sedimentary rock forms from compacted deposits. Metamorphic rock forms when existing rock is altered by heat and pressure.