Space physics

1. (a) Explain why places on the Earth have day and night, and state how long one cycle takes. [2]
2. (b) State the time taken for the Earth to orbit the Sun once. [1]
3. (c) State the approximate time taken for the Moon to orbit the Earth once. [1]
4. (d) Name the force that keeps the Moon in orbit around the Earth. [1]

1. (a) Which list shows four planets in order of increasing distance from the Sun?A Mercury, Venus, Earth, MarsB Venus, Mercury, Earth, MarsC Mercury, Earth, Venus, MarsD Mars, Earth, Venus, Mercury [1]

Lahore is in the northern hemisphere. Its summers are hot and its winters are cool.

1. (a) Explain why the Earth has seasons. [2]
2. (b) State the month in which Lahore has its summer, and explain why it is warmer then. [2]
3. (c) State what the season is in Australia when it is summer in Lahore. [1]

1. (a) List the types of object found in the Solar System. [3]
2. (b) Name the two largest planets, which are gas giants. [1]
3. (c) State what is meant by a natural satellite and give an example. [1]

The Earth orbits the Sun in an approximately circular orbit of radius 1.5 × 10¹¹ m. One orbit takes 365 days.

1. (a) Calculate the orbital speed of the Earth in m/s. Give your answer to 2 significant figures. [3]
2. (b) State the direction of the gravitational force on the Earth due to the Sun. [1]

The Moon orbits the Earth in an approximately circular orbit of radius 3.84 × 10⁸ m, taking 27.3 days for one orbit.

1. (a) Calculate the orbital speed of the Moon. Give your answer to 2 significant figures. [3]
2. (b) Explain why we see the Moon go through phases, such as crescent and full moon, during each orbit. [2]

Data for four planets:Mercury: mean distance from Sun 58 million km, orbital period 88 daysVenus: 108 million km, 225 daysMars: 228 million km, 687 daysJupiter: 778 million km, 4330 days

1. (a) Which statement is supported by the data?A The orbital period decreases as the distance from the Sun increases.B The orbital speed decreases as the distance from the Sun increases.C All four planets have the same orbital speed.D The orbital period is directly proportional to the distance from the Sun. [1]

The four planets closest to the Sun are small and rocky. The four outer planets are much larger and are made mostly of gases.

1. (a) Name the model that describes how the Solar System formed from a cloud of gas and dust. [1]
2. (b) Describe how the planets formed according to this model. [3]
3. (c) Explain why the inner planets are rocky while the outer planets are mainly gaseous. [2]

An astronaut has a mass of 72 kg. The gravitational field strength at the surface of Mars is 3.7 N/kg and at the cloud tops of Jupiter it is 24.8 N/kg.

1. (a) Calculate the astronaut's weight on Mars and on Jupiter. [2]
2. (b) State the astronaut's mass on Jupiter. [1]
3. (c) State two factors that determine the gravitational field strength at the surface of a planet. [2]

1. (a) Why does the Moon appear to change shape (show phases) during a month?A The Earth's shadow covers different parts of the Moon.B The Moon rotates on its own axis.C As the Moon orbits the Earth, we see different portions of its sunlit half.D The Moon gives out different amounts of light. [1]

The mean distance from the Sun to the Earth is 1.5 × 10¹¹ m. The speed of light and radio waves is 3.0 × 10⁸ m/s.

1. (a) Calculate the time taken for light from the Sun to reach the Earth, in minutes. [2]
2. (b) On one day the distance between Earth and Mars is 2.25 × 10¹¹ m. A controller sends a command to a rover on Mars. Calculate the shortest time before the controller can receive a reply confirming the command. [2]
3. (c) Explain why the time in (b) is different on other days. [1]
4. (d) Suggest why the rover is programmed to avoid obstacles by itself. [1]

A comet moves around the Sun in a very elongated elliptical orbit.

1. (a) State where in its orbit the comet travels fastest, and where slowest. [2]
2. (b) Explain your answer to (a) in terms of energy. [3]
3. (c) State how the strength of the Sun's gravitational field changes as the distance from the Sun increases. [1]

The International Space Station (ISS) orbits the Earth in an approximately circular orbit of radius 6.78 × 10⁶ m measured from the centre of the Earth. It completes one orbit every 92.7 minutes.

1. (a) Calculate the orbital speed of the ISS in km/s. Give your answer to 2 significant figures. [3]
2. (b) Calculate how many complete orbits the ISS makes in one day. [1]
3. (c) The Moon orbits much further from the Earth than the ISS. State and explain how the Moon's orbital speed compares with that of the ISS. [2]

1. (a) The Sun is a star. State the two elements it mainly consists of. [1]
2. (b) Describe the process that releases energy in the Sun. [2]
3. (c) Name the three regions of the electromagnetic spectrum in which the Sun radiates most of its energy. [2]

1. (a) The Milky Way is one of billions of galaxies in the Universe. What is its approximate diameter?A 100 light-yearsB 100 000 light-yearsC 100 million light-yearsD 13.8 billion light-years [1]

Objects in space: the Moon, the Sun, Proxima Centauri, the Andromeda galaxy.

1. (a) Place these objects in order of increasing distance from the Earth. [2]
2. (b) State what is meant by a galaxy. [1]
3. (c) Name the galaxy that contains the Sun. [1]
4. (d) Explain why distances to stars and galaxies are usually given in light-years rather than in metres. [1]

The speed of light is 3.0 × 10⁸ m/s. One year is 365.25 days.

1. (a) Define the light-year. [1]
2. (b) Calculate one light-year in metres. [2]
3. (c) Proxima Centauri, the nearest star to the Sun, is 4.2 light-years away. Calculate its distance in metres. [1]

1. (a) Describe the life cycle of a star with a mass similar to the Sun, starting from an interstellar cloud of gas and dust. [4]
2. (b) Explain why a star remains stable for most of its life. [2]

1. (a) Describe what is meant by the redshift of light from a distant galaxy. [2]
2. (b) Light from almost all distant galaxies is redshifted. State what this shows about the Universe. [1]
3. (c) Explain how this observation supports the Big Bang theory. [2]

1. (a) State what is meant by the cosmic microwave background radiation (CMBR). [2]
2. (b) Explain the origin of the CMBR. [2]
3. (c) State why the CMBR is evidence for the Big Bang theory. [1]

1. (a) What is the final stage in the life of a star with a mass similar to that of the Sun?A black holeB neutron starC white dwarfD red supergiant [1]

1. (a) Describe how a protostar forms. [2]
2. (b) State what must happen in the core for the protostar to become a stable star. [1]
3. (c) A stable star is described as being in equilibrium. Name the two opposing effects that are balanced. [2]

1. (a) Which statement about the cosmic microwave background radiation (CMBR) is correct?A It is emitted by the Sun.B It is detected from all directions in space and is evidence for the Big Bang.C It comes only from the centre of the Milky Way.D It is produced by stars that are forming now. [1]

Astronomers find the distance d to a distant galaxy and its speed of recession v.

1. (a) State how astronomers determine v. [1]
2. (b) State how astronomers determine d for a very distant galaxy. [2]
3. (c) A galaxy is at a distance of 9.0 × 10²⁴ m. Using H₀ = 2.2 × 10⁻¹⁸ per second, calculate its speed of recession and express it as a fraction of the speed of light (3.0 × 10⁸ m/s). [2]

1. (a) Describe what happens at the end of the life of a star that is much more massive than the Sun. [3]
2. (b) The explosion forms a nebula that contains hydrogen and many heavier elements. Explain what may happen to this material. [2]
3. (c) The Earth contains elements much heavier than iron, such as gold and uranium. Suggest what this tells us about the history of the material that formed the Solar System. [2]

Take the Hubble constant H₀ = 2.2 × 10⁻¹⁸ per second, 1 light-year = 9.5 × 10¹⁵ m and 1 year = 3.15 × 10⁷ s.

1. (a) A distant galaxy is moving away from the Earth at 1.5 × 10⁷ m/s. Calculate its distance from the Earth in metres. [2]
2. (b) Convert this distance into light-years. [1]
3. (c) Use the value of H₀ to estimate the age of the Universe in years. Give your answer to 2 significant figures. [2]

Astronomers measure the distance d and the speed v of recession of three galaxies.Galaxy P: d = 4.0 × 10²³ m, v = 9.0 × 10⁵ m/sGalaxy Q: d = 1.2 × 10²⁴ m, v = 2.6 × 10⁶ m/sGalaxy R: d = 2.5 × 10²⁴ m, v = 5.6 × 10⁶ m/s

1. (a) State the relationship between the speed of recession of a galaxy and its distance from the Earth that these data show. [1]
2. (b) Calculate v/d for each galaxy, then find the mean value of the Hubble constant H₀ from these data. Give your answer to 2 significant figures. [3]
3. (c) Using H₀ = 2.2 × 10⁻¹⁸ per second, predict the speed of recession of a galaxy at a distance of 3.6 × 10²⁴ m. [2]

Take 1 light-year = 9.5 × 10¹⁵ m and 1 year = 3.15 × 10⁷ s.

1. (a) The Andromeda galaxy is 2.5 million light-years from Earth. Calculate this distance in metres. [1]
2. (b) Explain what observing Andromeda today tells us about the light reaching our telescopes. [1]
3. (c) A space probe travels at 17 km/s. Estimate the time it would take to reach Proxima Centauri, 4.2 light-years away, in years. Give your answer to 2 significant figures. [3]

Take 1 year = 3.15 × 10⁷ s.

1. (a) Explain why the age of the Universe can be estimated as 1/H₀, where H₀ is the Hubble constant. [2]
2. (b) An older measurement gave H₀ = 1.6 × 10⁻¹⁸ per second. Calculate the age of the Universe this value would give, in years. Give your answer to 2 significant figures. [2]
3. (c) A student says that because nearly every galaxy is moving away from the Earth, the Earth must be at the centre of the Universe. Explain why this conclusion is not correct. [2]

1. (a) Light from galaxy X shows a larger redshift than light from galaxy Y. What can be concluded?A X is closer to the Earth than Y and moving away more slowly.B X is further from the Earth than Y and moving away faster.C X is moving towards the Earth.D X is hotter than Y. [1]