science at2

model

simplified way to represent something that may be too large, small or complex to study directly. some ADDVANTAGES: makes things that are hard to access easily accessible, study things up close that may be dangerous or rare, visualise complex systems. DISADVANTAGES: may not be accurate, doesnt react the way it would in real life, may miss certain details, may become outdated as organisms change.

geocentric

earth is in the centre, all planets orbit around EARTH

heliocentric

sun in midde, all planets orbit around SUN

why does gravity keep us around sun

sun is really heavy and has alot of gravitational force, but we also have gravitational force that keeps us from floating around

what is a star

a star is a luminous ball of gas, made mostly of hydrogen and helium

how is star held together

held together by its own gravity

all planets in order (remember mother and nachos!)

mercury, venus, earth, mars, jupiter, saturn, uranus, neptune

what are planets spinning on

planets always spinning on their axis

what is axis

invisible line around which object rotates

rotation

when a planet or moon turns/spins on its axis

what gives us day and night

rotation; when away from sun, night; when our country facing towards sun, day

whats a revolution

one revolution (orbit around sun or the body a planet is orbiting) is 365.25 days

why we got leap years

each year, we get a quarter of the day from the 365.25 days of each revolution and then it adds up every four years

why we have seasons

seasons happen because of the tilt/axis of earth (23.5 degrees). when in orbit, we are tilted, which means that sometimes the southern hemisphere tilts towards the sun (summer), and sometimes away from the sun (winter)

what is the moon

a satellite (something that orbits around a planet, moon or body) and its natural, since artificial ones are manmade and do things like take photos

what does moon do while orbiting

while the moon orbits earth, it slowly spins, just as earth spins while orbiting the sun, meaning that earth always sees moon

what are changes in the moon

phases of the moon

all phases of moon

New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third/Last Quarter, and Waning Crescent

what r tides

regular rises and falls of sea levels along coastline

how many high/low tides in 1 day along most coastlines

2 low tides, 2 high

reasons for tides

moons gravity pulls water away from Earth when a face of the earth and its coastlines are facing towards it (and also the oppisite side), making those coastline's water bulge towards moon. the coastlines in between are low tide since water is being pulled out of these areas

eclipse

special event when one celestial body passes through the shadow of another

total lunar eclipse

earth blocks light from moon (sequence is sun, earth, moon). earths shadow casts onto moon but the sunlight passes through earths atmosphere, which gives the moon a red or orange look

solar eclipse

moon passes between earth and sun, blocking sunlight from reaching certain areas on earth

annular solar eclipse

moon is further from earth, appearing smaller, which means that it doesnt cover all sun, leaving a ring of light around moon

total solar eclipse

moon completely covers sun, and the sky is dark for observers in the path of totality

path of totality

on earth where you can see the suns outer atomsphere during a total solar eclipse, and the sky is completely dark, in a twilight zone

partial solar eclipse

moon doesnt cover all the sun, only partially, and you can see some of the sun (around a half?)

partial lunar eclipse

part of the moon moves through earths shadow, making part of the moon red or dark, and the rest normal.

penumbral lunar eclipse

moon passes through earths penumbra shadow, and the result is very subtle, just a dimming of moon

force

push, pull, twist or turn in a particular direction

where does gravity pull

center of earth

forces can...

start an object moving, stop an object moving, change the direction in which an object is moving, change the shape of an object, change the speed of an object moving

how to represent direction of force

use arrows and put them in the direction the force is acting

contact force

forces that occur when in contact/ touching one another (friction, tension, air resistance)

indirect force

forces that occur between two objects not in physical contact, yet can exert a push or pull on each other (gravity, magnetic)

forces are...

vector quantities (they have magnitude, which is the size of force, and direction)

measurement of forces is called

Newtons (N)

what is a newton

one newton = amount of force required to push a one kg object to accelerate by one meter per second

how is force measured

spring balance or newton meter

velocity

speed and direction

an object will stay at rest...

unless acted on by an unbalanced force

for every action...

there is an opposite reaction

an object in motion will...

stay at the same speed + direction unless acted on by an unbalanced force (eg friction)

normal force

force which prevents objects from falling into what its sitting on. it is always perpendicular to the surface which an object is in contact with. it pushes up

drawing free body diagrams

put object in middle, the draw arrows FROM THE CENTRE in which the direction the different forces are heading

moon dreaming story for tides

the moon man in arnhem land fills up as the moon gets bigger, then at new moon and full moon 'lets the water out'

how do aboriginal people use stars to predict weather

emu in the sky and such; when it is in a certain position, they know the season and what to do and not to do. rapid twinkling also indicates more wind

how aboriginal people use stars to predict animal behaviour

eg emu in the sky; when it is in a certain position, it means the emus will be more defensive, and another will show it is okay to collect eggs. other constellations like this also show animal behaviour

energy

the ability to do work

work

when force is acted upon an object, causing it to move

3 key things for work

force, movement, cause

the force from the cause has to...

cause the movement of the object

formula for calculating work

work = force times distance

measurement unit of work

Joules (J)

measurement unit of force

Newtons (N)

distance unit measurement

metres (m)

distance calculation formula

distance = work divided by force

force calculation formula

force = work divided by distance

when to use bar graph

i.v. is words

when to use line graph

i.v. is numbers