Forces and the Universe
Forces
Distance-time graphs
Gravity
Day and night and seasons
Speed
The solar system
refers to the motion of an object
pushes or pulls
can be balanced or unbalanced
is the rate of change of distance- it is the distance travelled per unit time.
Vertical axis is the distance travelled from the start
Horizontal axis is the time travelled from the start
The force that pulls things to the ground
Holds earth and other planets in their orbits around the sun
A Star - the sun
Planets and dwarf planets orbit around the sun
We have day and night because the Earth rotates
The Earth takes 24 hours to do a complete turn
Sir Isaac Newton discovered gravity
Without gravity we would float
Gravity is much weaker on the moon
Very important force
When an object is stationary the line on the graph is horizontal
When an object is moving at a steady speed the line on the graph is straight but sloped
The steeper the line the greater the speed
Satellite moons in orbit around around most of the planets
Comet and asteroids in orbit around the sun
There are eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
The Sun's gravity keeps the planets in orbit
The planets take different amounts of time to move around the sun
Single orbit is called the planet's year
Comets are balls of ice and dust
Asteroids consist of rock and metal
At any time half of the earth faces the sun, this part has day. the other half receives no light and this has night
The sun is the source of light for day
The earth turning makes the sun look like it is moving
Day length is the time the sunrise to sunset when it is light
We have hot summers and cold winters because of the tilt of the earth's axis
When the Earth's axis points towards the sun it is summer in that hemisphere
When the Earth's axis points away it is winter
We have seasons because the earth is tiltes as it makes it journey around the sun
Spring, summer, autumn and winter
The height of the sun varies with the seasons
Three reasons for seasons 1. Tilt 2. Revolution 3. The north pole always points in the same direction
to measure speed, a distance value and a time value are needed
is a scalar quantity, as it doesn't refer to direction
you cannot see force, but often you can see what it does .
Contact force
Gravity
magnetism
forces due to static electricity
Friction