Forces And Motion: Astronomy

Question 0

What does gravitational force cause?

Answer 0

• Causes planets to orbit the sun.
• Causes the moon and artificial satellites to orbit the earth.
• Causes comets to orbit the sun.

Question 1

What does the moon orbit around?

Answer 1

The Earth.

Question 2

What is gravity?

Answer 2

A force that pulls you down towards the earth and also pulls the earth towards the sun.

Question 3

What does the gravitational force between two objects depend on?

Answer 3

Their masses and their distance apart.

Question 4

How is the gravitational force on two objects relative to the distance between them?

Answer 4

It’s inversely proportional to the distance squared - i.e. as the distance doubles the force gets four times smaller.

Question 5

How can you calculate orbital speed?

Answer 5

Average speed = distance moved/time taken
Distance moved would be circumference of the orbit so we can replace this with 2(Pi)r where r is the radius of the orbit.
So orbital speed = 2(Pi)*orbital radius/time period

Question 6

How are a comets orbits different to a planets?

Answer 6

A comet has an elliptical (oval-shaped) orbit around the sun.

Question 7

When will a comet travel fastest dusting its orbit?

Answer 7

Comets will travel fastest when they loop around the sun and then as they fly away the gravitational pull will decrease so they will move their slowest. It gains kinetic energy closest to the sun as that is where it is most pulled by gravity.

Question 8

What is a galaxy?

Answer 8

A collection of billions of stars.

Question 9

Which galaxy is the solar system part of?

Answer 9

The milky way galaxy.

Question 10

What is the universe?

Answer 10

A collection of billions of galaxies.

Question 11

How to remember the eight plants in order of distance from the sun?

Answer 11

My MERCURY
Very VENUS
Easy EARTH
Method MARS 
Just JUPITER
Speeds SATURN
Up URANUS
Naming NEPTUNE

Question 12

Where is the asteroid belt?

Answer 12

Between Mars and Jupiter

Question 13

Shape of the orbits of the planets

Answer 13

Elliptical (ovals) with the sun close to the centre

Question 14

What’s gravitational field strength?

Answer 14

The strength of gravity on a planet or moon
On Earth it is 10N/kg
On the moon it’s 1.7N/kg

Question 15

What does non luminous mean?

Example of non luminous object

Answer 15

They do not emit light

Eg the planets are non luminous objects: we see them because they reflect light from the sun

Question 16

How are the planets held in orbit?

Answer 16

By the gravitational pull of the sun (eg gravitational pull on Mercury is v large compared to neptunes- therefore Mercury follows a more tight curved path than Neptune)

Question 17

What are moons?

Answer 17

Natural objects that orbit a planet
Their motions (like planets) are determined by gravitational forces
They are also non luminous

Question 18

How long does it take the moon to orbit the Earth?

Answer 18

29.5 days (1 lunar month)

While orbiting the earth it also spins on its axis, and it also completes a rotation every 29.5 days

Question 19

Why do we always see the same half of the moon when looking up at the sky at night?

Answer 19

Because the time it takes to complete one orbit around the Earth is the same time for one rotation, the moon always keeps the same part of its surface facing the Earth

Question 20

What are comets?

Answer 20

Comets orbit the sun
Approx 1-30km in diameter
Made of dust and ice

Question 21

Describe a comets orbit?

Vague

Answer 21

Very elongated (v oval shaped)
At times they are very close to sun, at others they are at the outer reaches of the solar system

Question 22

Describe a comets orbit as it nears the sun?

Answer 22

The gravitational forces acting upon it increase and therefore it speeds up (whereas at the opposite end of the orbit it travels slowly)
They are most easily see near the sun

Question 23

what is the tail of the comet?

Answer 23

Made up of the melted ice carrying dust (due to heat of the sun)
It’s what we see when we see a comet from Earth
Therefore comets are most easily see when they are close to sun (their tales are largest)
The tail is always being pointed away form the sun (because it’s flow of melt stuff)