13 Astrophysics 4th Flashcards
What happens to the orbital speed of an child on a roundabout in a park if the child halves their distance to the centre of the roundabout?
v = 2πr / T
v is proportional to r
If radius is halved, orbital velocity is halved for the same time period.
What is a galaxy?
A large collection of stars- made of billions of stars rotating about a central point
What type of orbit does a comet have?
Very ellipitcal- with the Sun or star at one focal point.
What is the equation which links orbital speed, radius of orbit and time period?
orbital speed = 2π x radius / time period
v = 2πr / T
What is the unit for time period (T)?
seconds (s)
What is the unit for orbital speed?
metres per second
or kilometers per hour
What happens to the movement of a comet during one complete orbit?
A comet accelerates towards the star. The comet is travelling at its highest velocity as it whips round the star. As it moves away from the star it decelerates. At the furthest distance from the star the comet will be travelling at its slowest velocity.
What type of orbit does a satellite have?
Circular orbit around the Earth
In which position will the comet be travelling the fastest and why?
The comet travels the fastest at C because the gravitational pull is the largest at C.
Gravitational pull increases as distance between celestial objects decreases.
What happens to the orbital speed of an child on a roundabout in a park if the child halves the time period of the roundabout?
v = 2πr / T
v is inversely proportional to time period
If time period is halved, orbital velocity is doubled for the same radius.
What is the name of our galaxy?
The Milky Way
What is the universe?
A large collection of billions of galaxies
In which position will the comet be travelling the slowest and why?
The comet travels the slowest at A because the gravitational pull is the smallest at A.
Gravitational pull decreases as distance between celestial objects increases.
How many galaxies are found in the universe?
billions of galaxies
What is a geostationary orbit?
When a satellite is placed in high orbit above the equator with a speed such that its time period (T) is equal to 24 hours.
This means the satellite is always over the same point of the Earth- it can be used for satellite television.
In the image of a planet orbiting the Sun, how would you label the gravitational pull acting on the planet?
An arrow downward pointing towards the Sun
How could you calculate the orbital speed of a person standing on the very edge of a roundabout?
- Use a stopwatch to time 5 full rotations and divide this time by 5. This is the time for one revolution or the time period (T)
- Measure the radius (r) of the roundabout with a tape measure.
- Calculate orbital speed = 2πr/T
Which side of the orbital path is the comet accelerating? decelerating?
The comet accelerates from A to D to C since the gravitational pull is in the same direction as its movement. The gravitational pull is speeding it up.
The comet decelerates from C to B to A since the gravitational pull is in the opposite direction to its movement. The gravitational pull is slowing it down.
Which orbital path shows the orbit of a comet?
Blue or red?
- Blue orbital path
- Comets have elliptial orbits with time period of many years
Approximately how many stars are found in a galaxy?
billions of stars
