Satellites, gravity and circular motion Flashcards
What does every object do?
Every object in the Universe attracts every other object.These forces of attraction are usually only significent when they are on an astronomical scale.
Why are plantets in orbit?
Planets stay in orbit around the Sun because of gravitational attraction.
What is centripetal force?
Any object moving in a circle needs a force of attraction towards the centre of the circle. This is called centripetal force.
The larger the mass.
The greater the gravitational force.
The further away an object is.
The smaller the gravitational force.
What does gravitational force obey?
An inverse square law: force ∝ 1/force2.
The orbit time for a planet closer to the Sun is less because:
- The planet travels a shorter distance.
- The planet travels faster because there is a greater gravitational force.
How does a satellite move?
A satellite moves at a tangent and gravity makes it accelerate towards Earth.
How does a comet travel when travelling around the Sun?
Comets travel very quickly when close to the sun and very slowly when they are far away.
Where do polar satellites orbit?
Polar satellites orbit above the North and South pole just 100 km - 20 km above Earth.
How long is a polar orbit?
Most polar satellites orbit take 90 minutes to orbit the earth.
What can polar satellites see?
Polar orbit satellites can see the whole of the Earth’s surface as the Earth rotates beneath them.
Uses of a polar satellite.
They are used for imaging the Earth - including short range weather forecasting.
Where do geostationary satellites orbit?
A geostationary satellite orbits above the equator.
How long is a geostatonary orbit?
The time for one orbit is 24 hours - this means it always appears to be in the same position above the equator.
