Physics and Earth Science Revision Flashcards

Vocabulary flashcards covering physics motion, dynamics, energy, and Earth system cycles based on the lecture notes.

Acceleration

The rate of change in velocity per unit of time.

Air resistance

Friction between the air and a moving object.

Average speed

A measure of how fast something moves on average.

Displacement

A measurement of the change in position of a moving body; a straight line connecting the start and end points is specified in terms of length and direction.

Distance

A measurement of how far objects are.

Gradient

The slope of a line on a graph, calculated as $\text{rise}/\text{run}$.

Instantaneous speed

The speed of an object at a particular moment.

Reaction Distance

The distance moved while reacting to an emergency.

Reaction Time

The length of time it takes a driver to respond to a hazard.

Speed

The rate of change of distance.

Terminal Velocity

The final velocity that an object falls with when no further acceleration is possible due to air resistance.

Velocity

The rate of change of displacement.

Fixed cameras

Speed measuring devices operating using two electronic sensors embedded in each lane of a road to determine speed by timing travel between sensors.

Motion sensors

Devices that send out pulses of radiation (such as ultrasonic sound waves, microwaves, or infrared radiation) and use reflection data to determine an object's position and speed.

Ticker timer

A device attached to an object moving in a straight line that records its motion as dots on paper tape, where dots closer together indicate slower speed and dots further apart indicate acceleration.

Driver reaction time range

For a person who is on high alert and concentrating while driving, reaction time is typically $0.15 - 0.30\text{ seconds}$.

Braking distance

The additional distance covered by a car as it comes to a stop after the driver has reacted and applied the brakes.

Total stopping distance

The total distance taken to stop a car, which is the sum of the reaction distance and the braking distance.

Acceleration due to gravity

The rate at which a falling object accelerates towards Earth, equal to $9.8\text{ m/s}^2$ (increasing speed by almost $10\text{ m/s}$ or $36\text{ km/h}$ for every second it falls).

1 g

A unit of acceleration equal to $9.8\text{ m/s}^2$.

Distance-time graph

A graph showing how far an object travels as time progresses; a flat line indicates stopped motion and a steeper slope represents faster speed.

Displacement-time graph

A graph plotting an object's displacement on the vertical axis against time on the horizontal axis.

Speed-time graph

A graph showing how speed changes over time; acceleration is shown by the slope (gradient), a flat horizontal line shows constant speed, and a negative slope shows deceleration.

Inertia

The tendency of an object to resist changes in motion.

Newton's first law of motion

An object at rest will remain at rest unless acted upon by an unbalanced force; an object that is moving will continue moving unless acted upon by an unbalanced force.

Newton's second law of motion

An object will accelerate in the direction of an unbalanced force acting upon it such that $F = ma$.

Newton's third law of motion

For every action, there is an equal and opposite reaction.

Reaction force

The equal and opposite force exerted back onto an object when an action force is applied, such as the force felt when hitting a cricket ball with a bat.

Efficiency

A measure of the useful energy output of an energy transfer.

Elastic potential energy

Energy stored in a stretched or compressed material, such as a spring or elastic band.

Gravitational potential energy

The potential energy possessed by an object due to its position above the ground.

Kinetic energy

The energy of a moving body.

Law of conservation of energy

Energy may be transferred or transformed, but it is never created or destroyed.

Potential energy

Energy possessed by an object because of its position or structure; also called stored energy.

Kinetic Energy formula

The equation $E_k = \frac{1}{2}mv^2$, where $E_k$ is kinetic energy, $m$ is mass of the object, and $v$ is speed of the object.

Gravitational Potential Energy formula

The equation $E_p = mgh$, where $E_p$ is gravitational potential energy in $\text{J}$, $m$ is mass in $\text{kg}$, $g$ is gravitational field strength in $\text{N/kg}$, and $h$ is height in $\text{m}$.

Acceleration formula

The equation $a = \frac{v - u}{t}$, where $a$ is acceleration, $v$ is final velocity, $u$ is initial velocity, and $t$ is time taken.

Energy Efficiency formula

The relationship given by $\frac{\text{Energy Output}}{\text{Energy Input}} \times 100 = \text{\text{\% Efficiency}}$.

Scalar quantity

A quantity, such as distance or time, that has magnitude (size) but no direction.

Vector quantity

A quantity, such as displacement or velocity, that has magnitude (size) and direction.

Atmosphere

The layers of gases surrounding the planet.

Biosphere

All living things on Earth; the sum of all Earth's ecosystems.

Hydrosphere

All liquid water on the Earth's surface.

Lithosphere

The land masses on Earth.

carbon cycle

The process by which carbon is recycled through the soil, water, living things, and the atmosphere.

Nitrogen cycle

The process by which nitrogen cycles between the living and non-living environments.

Fossils

The preserved remains of once-living organisms.

Fossil fuels

Fuels that contain the carbon of plants and animals that died and were preserved millions of years ago.

Liquefaction

A process in which saturated, sandy soils lose their strength during earthquake compression and behave like liquids.

Nitrogen-fixing bacteria

Bacteria that absorb nitrogen from the air and convert it into ammonia and then into nitrates.

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize glucose from carbon dioxide and water, represented by $6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$.

Respiration

The process occurring within living cells by which chemical energy is released from glucose using oxygen, represented by $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}$.

Sustainable ecosystems

Ecosystems that are diverse and provide for the needs of the organisms that live there.

Nitrogen fixation

The process in the roots of plants where nitrogen gas from precipitation or soil is combined with hydrogen by bacteria to create ammonia.

Nitrification

The biological process in which bacteria combine ammonia with oxygen to produce nitrites ($\text{NO}_2^-$), which are then converted by additional nitrifying bacteria into nitrates ($\text{NO}_3^-$).

Assimilation

The process by which plants absorb and utilize nitrates from the soil.

Ammonification

The process where decomposers in the soil break down animal waste or dead bodies to return nitrogen to the cycle as ammonium ($\text{NH}_4^+$).

Denitrifying bacteria

Bacteria that convert soil nitrates back into atmospheric nitrogen gas, releasing it into the air.

The Hydrologic Cycle (Water Cycle)

A series of flows of water between various water stores and storages on, above, and below Earth's surface.

Condensation

Water vapor in the atmosphere cooling and changing back into liquid water, forming clouds.

Precipitation

The process of water falling onto the Earth's surface through rain, snow, or hail.

Evaporation

Liquid water turning into gas or vapor through the heat of the sun.

Transpiration

The process in which plants absorb water from their roots and transfer it to their leaves, where it evaporates into water vapor.

Percolation

Water sinking into the ground, passing through bedrock, and entering underground aquifers.

Greenhouse effect

The natural warming of Earth caused by greenhouse gases absorbing outgoing long-wave radiation and re-emitting it in all directions.

Climate

The long term averages of weather conditions.

Weather

The short-term conditions in the atmosphere, including wind, cloud, and precipitation.

Gyres

The circular surface ocean current patterns shown in major ocean basins, driven by wind and Earth's rotation.

Thermohaline circulation

The scientific term for the global conveyor belt; a continuous, deep ocean circulation driven by temperature and salinity differences that takes about $1600\text{ years}$ to complete one circuit.

Enhanced greenhouse effect

An increase in the natural greenhouse effect caused by human activities increasing atmospheric concentrations of carbon dioxide, methane, and nitrous oxide.

Carbon dioxide emission proportion

Accounts for $76\%$ of total human greenhouse gas emissions, making it the most abundant human-emitted greenhouse gas.

Atmospheric lifespan of carbon dioxide

Persists in the atmosphere for hundreds to thousands of years, making its removal a long-term challenge.

Primary cause of carbon dioxide accumulation

Human activities such as fossil fuel combustion and deforestation release $CO_2$ faster than natural carbon sinks can absorb it.

Methane warming potency and lifespan

Traps $20 \times$ more heat than $CO_2$ over a 100-year scale, with an atmospheric lifespan of approximately $12\,\text{years}$.

Primary sources of methane emissions

Livestock digestion, rice paddies, coal mines, oil fields, landfill decomposition, and thawing permafrost.

Nitrous oxide heat-trapping capacity

Traps $300 \times$ more heat than $CO_2$ and has increased in concentration by $18\%$ since the pre-industrial era.

Primary sources of nitrous oxide emissions

Synthetic fertilizer application, automotive exhaust, and the burning of nitrogen-containing materials.

Sulfur dioxide climate impact

Exerts a net cooling effect on climate by reflecting incoming sunlight, though it causes acid rain and atmospheric pollution.

Fluorinated gases warming potential

Synthetic gases from refrigeration and aerosols that trap heat thousands of times more effectively than $CO_2$ and deplete the ozone layer.

Carbon sink

Any natural or artificial reservoir, such as oceans, forests, or soil, that absorbs more carbon from the atmosphere than it releases.

Ocean acidification cause

Occurs when oceans absorb excess atmospheric $CO_2$, forming carbonic acid which lowers seawater pH and harms marine organisms like corals and shellfish.

Salt rejection during sea ice formation

Process where freezing sea water expels salt into surrounding ocean water, creating dense, highly saline water that sinks to drive thermohaline circulation.

Antarctic ice albedo effect

Large surface ice sheets reflect incoming solar radiation back into space, preventing ocean warming through high albedo.

Water temperature effect on ocean carbon absorption

Warmer ocean water holds less dissolved $CO_2$ than cold water, reducing the ocean's capacity to act as a carbon sink as temperatures rise.

Permafrost-methane feedback loop

Thawing permafrost releases stored methane gas, which accelerates atmospheric warming and leads to increased permafrost thawing.

Ice-albedo feedback loop

Melting ice reduces Earth's reflective surface, causing higher heat absorption by dark ocean or land, which accelerates ice melting.

Ocean acidification feedback loop

Absorbed $CO_2$ acidifies ocean waters, harming carbon-absorbing plankton and leaving a higher proportion of $CO_2$ in the atmosphere.

Forest dieback feedback loop

Warming temperatures dry out forests, triggering intense wildfires that release stored $CO_2$ into the atmosphere and intensify warming.

Main challenge in attributing climate change to human activity

A lack of direct observational climate data beyond $100\,\text{years}$ ago makes distinguishing human influence from natural climate variability difficult.

Southern Oscillation Index (SOI)

A metric measuring atmospheric air pressure differences between Tahiti and Darwin used to identify El Niño and La Niña climate phases.

El Niño climate phase

Occurs when Pacific trade winds weaken, keeping warm surface waters in the eastern Pacific and causing drought and dry conditions in Australia.

La Niña climate phase

Occurs when Pacific trade winds strengthen, pushing warm water toward Australia and increasing evaporation, cloud cover, and rainfall