Nagano 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 acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass: F = ma.

Velocity versus speed

Speed is the distance traveled per unit time and has no direction. Velocity is speed in a stated direction, so a change in direction changes velocity.

Balanced forces

Balanced forces have equal size and opposite direction, so the net force is zero. An object at rest stays at rest, and a moving object keeps constant velocity.

Kinetic energy formula

Kinetic energy equals one half times mass times speed squared: KE = 1/2 mv^2. Doubling speed quadruples kinetic energy for the same mass.

Conservation of energy

Energy cannot be created or destroyed in an isolated system; it changes form. For example, gravitational potential energy becomes kinetic energy as an object falls.

Ohm's law

For a metallic conductor at constant temperature, current equals voltage divided by resistance: I = V/R. Increasing resistance reduces current for a fixed voltage.

Series circuit rules

In a series circuit there is one path. Current is the same through every component, voltage divides among components, and total resistance equals the sum of resistances.

Wave equation

Wave speed equals frequency multiplied by wavelength: v = f λ. Frequency is hertz, wavelength is metres, and speed is metres per second.

Sound needs a medium

Sound is a longitudinal wave that travels by particle vibrations. It needs a material medium such as air, water, or steel and cannot travel through a vacuum.

Density formula

Density equals mass divided by volume: ρ = m/V. An object floats in a fluid when its average density is less than the fluid's density.

Particle model of gases

Gas particles are widely spaced and move rapidly in random directions. They collide with container walls, creating pressure, and their average speed increases with temperature.

Law of conservation of mass

In a chemical reaction, the total mass of reactants equals the total mass of products because atoms are rearranged, not created or destroyed. Equations must be balanced.

Exothermic reaction

An exothermic reaction releases energy to the surroundings, usually as heat, so the surroundings warm up. Combustion and neutralization are common examples.

Atomic number

The atomic number of an element is the number of protons in one atom of that element. It determines the element's identity and its position in the periodic table.

Molecule versus compound

A molecule is two or more atoms chemically bonded together. A compound is a substance made of atoms of different elements chemically combined, such as water, H2O.

Ionic bond formation

An ionic bond forms when a metal atom transfers electrons to a nonmetal atom, creating oppositely charged ions that attract each other in a lattice.

Neutralization reaction

An acid reacts with a base to form a salt and water. In terms of ions, hydrogen ions from the acid combine with hydroxide ions from the base.

Alveoli function

Alveoli are tiny air sacs in the lungs with thin, moist walls and a large surface area. Oxygen diffuses into blood and carbon dioxide diffuses out.

Artery versus vein

Arteries carry blood away from the heart under high pressure and have thick elastic walls. Veins carry blood toward the heart under low pressure and contain valves.

Meiosis purpose

Meiosis produces gametes with half the normal chromosome number. Fertilization restores the diploid number, and crossing over creates genetic variation in offspring.

Dominant allele

A dominant allele is expressed in the phenotype even when only one copy is present. A recessive allele is expressed only when two recessive copies are inherited.

Osmosis definition

Osmosis is the diffusion of water across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.

Mitochondria role

Mitochondria are organelles where aerobic respiration releases energy from glucose. Cells that need large amounts of energy, such as muscle cells, contain many mitochondria.

Cell membrane function

The cell membrane is a selectively permeable barrier that controls which substances enter or leave the cell and helps maintain a stable internal environment.

Food chain arrows

In a food chain, arrows show the direction of energy transfer from one organism to the next. They point from the producer or prey toward the consumer or predator.

Decomposer role

Decomposers break down dead organisms and waste, releasing nutrients such as nitrogen and minerals back into the soil for producers to reuse.

Law of superposition

In undisturbed sedimentary rock layers, the oldest layer is at the bottom and the youngest is at the top. This principle gives relative ages of strata.

Index fossil use

An index fossil comes from a species that lived over a short time but had a wide geographic distribution. It helps match rock layers of the same age.

Troposphere characteristics

The troposphere is the lowest atmospheric layer and contains most water vapor and weather. Temperature generally decreases with height in this layer.

Air pressure and altitude

Air pressure decreases as altitude increases because there is less air above. Air moves from higher pressure toward lower pressure, producing wind.

Cause of seasons

Earth's axis is tilted about 23.4 degrees. As Earth revolves around the Sun, different hemispheres receive more direct sunlight, causing the seasons.

Moon phases cause

Moon phases depend on the changing angle between the Sun, Earth, and Moon. Half the Moon is always sunlit, but we see different portions from Earth.