Topic 8: Space

Question 1

Describe the life cycle of a Star

Answer 1

• stars form from clouds of dust and gas - nebula
• a protostar is formed when gravity pulls the dust and gas together, there’s an increase in temperature and fusion takes place
• during fusion, helium nuclei fuse to make heavier elements
• a main sequence star is then formed and is stable as the force of gravity inwards is in equilibrium with the outwards pressure due to nuclear fusion - during this iron is formed
• a main sequence star then expands to form a red super giant (if bigger than the sun)

Question 2

What is the orbital period?

Answer 2

Time it takes/ how long it takes to orbit an object

Question 3

Why are satellites always accelerating?

Answer 3

• gravity causes satellite to accelerate towards the Earth
• speed is constant
• change in direction causes velocity to constantly change
• if velocity changes, it’s accelerating

Question 4

What does it mean when ‘the universe seems to be expanding?’

Answer 4

Galaxies seem to be moving away from each other

Question 5

How do we find that the wavelength has increased from distant galaxies?

Answer 5

We look at the light from most distant galaxies

Question 6

What do we mean by the term red-shift?

Answer 6

• the wavelengths are all longer than they should be
• they’re shifted towards the red end of the spectrum
• this is called red-shift

Question 7

What does red-shift suggest?

Answer 7

The source of the light is moving away from us
Measurements of the red-shift indicate that these distant galaxies are moving away from us (receding) very quickly

Question 8

What does it mean when ‘more distant galaxies have greater red-shifts than nearer ones?’

Answer 8

More distant galaxies are moving away faster than nearer ones

Question 9

How does instantaneous velocity affect the object whilst orbiting?

Answer 9

• object keeps accelerating towards what it’s orbiting
• but the instantaneous velocity (right-angled to acceleration) keeps it travelling in a circle

Question 10

Where does the gravitational force need to be between for orbiting to occur?

Answer 10

• force that makes this happen is produced by the gravitational force
• which is between the planet and the sun (or between the planet and its satellites)

Question 11

What does the size of the orbit depend on?

Answer 11

The object’s speed

Question 12

Why does the size of the orbit depend on speed?

Answer 12

• The closer you get to a star or planet, the stronger the gravitational force is
• the stronger the force, the faster the orbiting object needs to travel to remain in orbit (to not crash into the object that it’s orbiting)

Question 13

Describe what happens for an object in a stable orbit

Answer 13

• for an object in a stable orbit, if the speed of the object changes, the size (radius) of its orbit must do so too
• faster moving objects will move in a stable orbit with a smaller radius than slower moving ones

Question 14

What is the solar system?

Answer 14

All things that orbit the sun

Question 15

What are planets?

Answer 15

Large objects that orbit a star

Question 16

What are dwarf planets?

Answer 16

Planet-like objects that orbit stars, but don’t meet all of the rules for being a planet

Question 17

What is the moon an example of and what does it do?

Answer 17

Moons orbit planets. The moon is an example of a natural satellite (not man-made)

Question 18

What are artificial satellites?

Answer 18

Satellites that humans have built (generally orbit the earth)

Question 19

What force is needed to create orbits?

Answer 19

Gravity

Question 20

How do planets orbit the sun?

Answer 20

Planets move around the sun in almost circular orbits

Question 21

What does it mean if an object is travelling in a circle?

Answer 21

• if an object is travelling in a circle, it is constantly changing direction
• which means it is constantly accelerating
• also means it is constantly changing velocity, but NOT changing speed

Question 22

What conditions must there be for an object to accelerate?

Answer 22

There must be a force acting on an object for it to accelerate

Question 23

How does the force affect the object?

Answer 23

• force would cause the object to fall towards whatever it was orbiting
• but because the object is already moving, it just causes it to change direction