TOPIC 7 - ASTRONOMY Flashcards
What is weight?
Force on an object due to gravitational attraction, depending on mass and gravitational field strength.
What does gravitational field strength depend on
mass of body and distance from
centre-> surface
Equation for weight?
mass x g
What is order of planets in our solar system?
- Sun
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
What does our solar system consist of?
- The sun
- Planets (orbiting Sun)
- Planets’ natural satellite
- Dwarf planets
- Asteroids+comets
What is geocentric model?
Used to think everything revolved around Earth
Why did people believe geocentric model at the time?
There was only naked eye evidence at the time.
Sun and Moon seemed to move across the sky in same direction and motion everyday.
Rule of orbit
Smaller body orbits larger body
What do planets orbit + how?
The sun.
They all orbit in the same plane + same direction around sun.
Orbit at different distances from sun and at different speeds (planets furthest away travel slower)
What do moons orbit + how?
Planets.
They orbit in circular motion.
They have more speed when closer to planet.
What do comets orbit + how?
The sun.
Highly eliptical (stretched) orbits.
Speed of comets change as distance from sun changes.
What are artificial satellites used for?
Communications, research of earth + space
How to maintain a stable orbit?
Gravitational force on low orbit satellite needs to be higher than a satellite in high orbit. A low orbit satellite needs to move faster to stay in its orbit. All satellites must be at correct speed to reach circular orbit.
If speed increases, radius must increase also.
If speed decrease, radius must decrease.
What happens if a satllite moves too slow or fast?
Too slow = fall towards Earth as the gravitational attraction is too strong
Too fast = spirals out into space as the gravitational attraction cannot provide enough force.
What is the Doppler effect?
Change in wave frequency during relative motion between a wave source and its observer.
