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GCSE Physics > 4.8 Space > Flashcards

4.8 Space Flashcards

1
Q

Explain why the Sun will not go through the supernova stage but the star Mira will

A

Only very massive stars become a supernova. The Sun is not as big as the star Mira.

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2
Q

To stay in its present orbit around the Earth, each satellite must move at a particular…?

A

speed

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3
Q

Describe the orbit of an artificial satellite

A

circular

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4
Q

How is the star Mira different to the Sun?

A

The star Mira is much more massive

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5
Q

Describe how stars are formed

A

Enough dust and gas from Space are pulled together by gravitational attraction

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6
Q

State why a star is stable during the ‘main sequence’ period of it’s life cycle

A

forces within it are balanced

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7
Q

acceleration

A

rate of change of velocity on an object

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8
Q

velocity

A

how fast you are going in a certain direction

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9
Q

centripetal force

A

When an object moves in a circle at a constant speed, its direction of motion is constantly changing, so the velocity is also changing. Acceleration is the rate of change of velocity so the object must be accelerating. This means a force must be acting on the object. The force causing circular motion is centripetal force, and it acts towards the centre of the circle.

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10
Q

What does the magnitude of the centripetal force depend on?

A
  • orbital radius decreases - object is changing direction more quickly & needs a greater CF to produce a greater acceleration
  • object of greater mass
  • object is moving at a greater speed
    all need a greater centripetal force to keep it moving in a circle
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11
Q

The Moon orbiting the Earth

A

Another example of circular motion. The gravitational attraction between the Moon and the Earth is the centripetal force. The size of the centripetal force depends on the speed, mass, and the radius of the circle the object is travelling around.

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12
Q

Earth orbiting the Sun

A

The Earth’s orbit is elliptical (oval-shaped path). The force of gravity acting between the Sun and the Earth holds Earth in its orbit.

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13
Q

satellites (natural)

A

A satellite is a object that orbits another larger, or more massive, object in space. The moon has a circular orbit around the Earth, and is a natural satellite. The force of gravity holds the Moon in its orbit. Examples of natural satellites are the Moon and the Earth.

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14
Q

satellites (artificial)

A

Artificial satellites are man-made. Examples are TV satellites and satellites used for imaging. The force of gravity is changing the velocity but not the speed.

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15
Q

Explain why for a stable orbit, the radius of orbit must change if the speed changes

A

At a higher speed, object requires a greater centripetal force → a greater force of gravity/gravitational attraction, to prevent it flying off into space. By decreasing the orbital radius, the gravitational force on the object is greater, and the object remains in a stable orbit.

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16
Q

Explain how the force of gravity acting on a satellite affects its speed and velocity

A

The force of gravity can change its velocity since the direction is constantly changing, but it can’t cause a change of speed since there is no force component in the direction of motion.

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17
Q

‘A star forms when enough dust and gas are pulled together. Masses smaller than a star may also be formed when dust and gas are pulled together’. The smaller masses may be attracted by the star and become….

A

planets

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18
Q

what is a geosynchronous orbit

A

when the orbital period of the satellite is equal to the rotational period of the Earth (24 hours). It does not stay at the same place above Earth.

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19
Q

what is a geostationary orbit

A

A geostationary orbit is a type of geosynchronous orbit. The difference is that GS goes right around the Equator and only the Equator. The satellite will always stay above the same place on Earth. Geostationary satellites have a higher altitude, and orbit slower as there is a lower centripetal force/ greater circumference for the same speed

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20
Q

what is a polar orbit

A

polar orbits go from north pole to south pole. They are close to Earth (low altitudes). One orbit is approximately 90 minutes.

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21
Q

what are polar orbits used for?

A

a monitoring satellite, such as weather forecasting, spying

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22
Q

what are geostationary satellites used for?

A

global positioning systems, communications

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23
Q

Explain why a satellite has a constantly changing velocity even though it moves at a constant speed

A

Velocity is a vector (has size and direction). Satellite may move at the same speed but its direction is constantly changing as it moves in a circle

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24
Q

example of a smaller satellite orbiting a larger and more massive object

A

a planet/comet orbiting the Sun OR an artificial satellite orbiting the Earth

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25
Q

example of a larger satellite orbiting a smaller but more massive object

A

a planet/star/ galaxy orbiting a black hole

26
Q

what are produced during the fusion processes in a star?

A

all the naturally occurring elements

27
Q

suggest why scientists cannot give the exact number of years a star will be in the ‘main sequence’ period

A

not enough evidence

28
Q

Explain why the rate of nuclear fusion in a large star is faster than in a small star

A

Large stars have a shorter ‘main sequence’ period so they have a faster rate of nuclear fusion

29
Q

Explain how stars produce energy

A

lots of reactions occur and nuclei/atoms of light fuse

30
Q

What evidence is there to suggest that the Sun was formed from the material produced when an earlier star exploded?

A

presence of nuclei of heavy elements

31
Q

What is a black hole?

What is produced as the gases from a star spiral into a black hole?

A

a mass with such a strong gravitational field that light is pulled in
- x-rays

32
Q

What is a supernova?

A

explosion of a star

33
Q

Where did the elements form?

A

stars

34
Q

Explain why mass is the only thing that affects the force acting on a geostationary satellite?

A

radius is fixed so speed is fixed

35
Q

What provides the centripetal force? (rubber bung)

A

tension in the string

36
Q

One student swung the rubber bung around in a circle at a constant speed. The second student timed how long it took the rubber bung to complete 10 rotations. The students then calculated the speed of the rubber bung, using the radius of the circle and the time to complete one rotation. The students repeated this for several different values of centripetal force.

Explain why the radius of the circle and the mass of the rubber bung were not changed in the experiment.

A

each may also affect the speed/results and there’s only one independent variable

37
Q

Suggest why the students times 10 rotations of the rubber bung, rather than just one rotation.

A

reduces timing error (for 1 rotation)

38
Q

Explain why in polar orbits the force is bigger

A

polar orbits are closer to the Earth so bigger pull of gravity

39
Q

Explain why the star remains stable for millions of years in the main sequence period (2)

A

radiation ‘pressure’ and gravity are balanced, and there is sufficient hydrogen to last a long time

40
Q

Explain how stars like the Sun were formed (2)

A

from a giant cloud of gas or hydrogen that condensed

41
Q

Why is fusion important?

A

fusion is an energy producing process

42
Q

Over billions of years the amount of hydrogen in a star decreases. Why?

A

converted into helium

43
Q

The inner planets of the solar system contain atoms of the heaviest elements that come from a supernova. What does this tell us about the age of the solar system compared with many
of the stars in the Universe?

A

younger

44
Q

What happens to cause the stable period in the life cycle of a star to end?

A

runs out of hydrogen

45
Q

The diagram, drawn below, places stars in one of four groups.
Where a star is placed on the diagram is determined by the surface temperature and
relative luminosity of the star.
A star with a relative luminosity of 1, emits the same amount of energy every second as
the Sun.
Use the information in the diagram to describe what will happen to the Sun after the
stable period ends. (3)

A

temperature decreases and the relative luminosity increases as it changes to a red giant. The temperature increases and the relative luminosity decreases as it changes to a white dwarf.

46
Q

Explain how atoms of the element helium (He) are formed in a star. (2)

A

fusion of hydrogen

47
Q

Explain how atoms of very heavy elements, such as gold (Au), were formed. (2)

A

fusion of other elements during supernova

48
Q 
Explain how, and when, atoms of different elements may be distributed throughout
the Universe(2)
A

supernova when stars ‘die’

49
Q

Describe what will happen to a star, originally much more massive than the Sun,
after it reaches its red giant stage. (2)

A

explodes as a supernova and elements were distributed through Space

50
Q

Shortly after the ‘big bang’, hydrogen was the only element in the Universe.
Explain how the other elements came to be formed. (3)

A

by nuclear fusion of hydrogen to helium, and the elements heavier than iron are only produced in a supernova

51
Q

Explain the difference between a protostar and a main sequence star. (2)

A

a protostar is at a lower temperature as (nuclear) fusion reactions have not started

52
Q

Describe the process of nuclear fusion(1)

A

joining of 2 atomic nuclei to form a larger one

53
Q

The Universe now contains a large variety of different elements.
Describe how this happened(4)

A
  • fusion takes place within stars
  • hydrogen formed into helium
  • fusion continued and formed larger elements
  • elements heavier than iron were formed in supernova
54
Q

What is the relationship between the masses of the dust and gas in the cloud in
Stage 2 and the force of gravity between them? (1)

A

the bigger the masses (of the dust and gases then) the bigger
the force

55
Q

What is the relationship between the distance apart of the dust and gas in the cloud in
Stage 2 and the force of gravity between them? (1)

A

the greater the distance (between the dust and gases then) the
smaller the force

56
Q

The inner planets of the solar system contain atoms of the heaviest elements.
(i) Where did these atoms come from? (1)

A

supernova

57
Q

Why is energy released by such nuclear fusion reactions? (2)

A

the mass of the large nucleus (atom) is less than the mass of the smaller
nuclei, and the mass loss converted into energy or small mass loss given a large amount of energy

58
Q

At the end of the stable stage of its life a star will change.
Describe and explain the changes that could take place(6)

A

hydrogen is used up and the star will expand and become a red giant. It will contract under gravity and become a white dwarf. It may explode and become a supernova throwing dust and gas into space
leaving a dense neutron star / black hole.

59
Q

How is it possible to detect a black hole? (2)

A

x-rays emitted when gases or matter released from nearby stars spiral into it

60
Q

The changes which happen in stars result in new elements being formed.
Nuclei of the heaviest elements are found in the Sun.
Describe how these nuclei are formed (2)

A

fusion (of nuclei) of lighter elements

61
Q

The Sun contains nuclei of the heaviest elements. Atoms of these heaviest elements are
also present in the planets of the solar system. What does this suggest about the material
from which the solar system is formed?(1)

A

materials produced when earlier stars

exploded

GCSE Physics (2 decks)

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