IGCSE Physics 0625 — Topic 6: Space Physics — Paper 2 (MCQ) Cambridge Challenge 2

Question 1

An observer watches the night sky for several hours from a fixed spot.

The stars appear to move across the sky from east to west. Why?

AThe Earth spins from west to east on its axis, carrying the observer round, so the whole sky appears to travel the opposite way BThe stars themselves all orbit around the Earth once each day, travelling together from the eastern horizon across the top of the sky and over to the western horizon CThe Earth’s orbit around the Sun sweeps the observer past the stars once every twenty-four hours of the night DLight from the stars is bent gradually westwards as it passes through the moving layers of the atmosphere

Question 2

The Moon does not produce its own light, yet a full Moon is bright in the night sky.

Why can the Moon be seen?

AIt glows because its surface is still hot from the collisions that formed it billions of years ago BIt focuses starlight from behind it towards the Earth in the way that a large curved mirror would CIt reflects sunlight towards the Earth, and at full Moon the whole of its Earth-facing side is lit by the Sun DIt produces its own light by the same nuclear fusion process as the Sun does, but far more weakly because it is very much smaller and cooler

Question 3

The Earth rotates through 360° in approximately 24 hours.

Through what angle does it rotate each hour, and what everyday observation does this cause?

A360° per hour, which is why the Sun appears to flash past repeatedly during a single afternoon B24° per hour, which causes the seasons to change progressively through the course of the year C15° per hour, which causes the Sun’s apparent position to move steadily across the sky during the day D15° per hour, which causes the Moon to change its phase from night to night through the month

Question 4

In summer at a given location the Earth’s axial tilt points that hemisphere towards the Sun.

Which pair of effects makes summer days warmer than winter days?

AThe Earth moves significantly closer to the Sun during the summer months, and it also travels more slowly along its orbit while it is in the nearby part BThe atmosphere becomes thinner in summer, letting through more of the sunlight, and the days also become longer CThe Sun itself releases more energy during the summer months, and the Earth also spins more slowly then DThe Sun climbs higher in the sky, so its energy is spread over less ground area, and daylight lasts longer each day

Question 5

Which row gives the approximate time for each motion?

AEarth spinning once on its axis: 24 hours; Moon orbiting the Earth: about 365 days; Earth orbiting the Sun: about 1 month BEarth spinning once on its axis: about 365 days; Moon orbiting the Earth: about 1 month; Earth orbiting the Sun: 24 hours CEarth spinning once on its axis: about 1 month; Moon orbiting the Earth: 24 hours; Earth orbiting the Sun: about 365 days DEarth spinning once on its axis: 24 hours; Moon orbiting the Earth: about 1 month; Earth orbiting the Sun: about 365 days

Question 6

One week after a full Moon, an observer looks at the Moon again.

What does the observer see, and why?

AAbout half of the Moon’s disc is lit, because the Moon has completed roughly a quarter of its orbit around the Earth BAbout half of the Moon’s disc is lit, because the Earth’s shadow is covering the other half of the disc CAnother completely full Moon, because the Moon’s appearance only ever changes gradually over the course of a complete year of observations DA completely dark new Moon, because one week is the exact time needed for half of the Moon’s orbit

Question 7

The Earth orbits the Sun in an approximately circular orbit of radius 1.5 × 10¹¹ m, taking one year (3.2 × 10⁷ s).

What is the Earth’s average orbital speed?

AAbout 4.7 × 10³ m/s BAbout 3.0 × 10⁴ m/s CAbout 3.0 × 10⁶ m/s DAbout 4.7 × 10⁹ m/s

Question 8

From one month to the next, the constellations visible at midnight change gradually, returning to the same view after a year.

What causes this annual cycle?

AAs the Earth moves around its orbit, the night side of the Earth faces out towards a different part of the sky each month BThe Earth’s axis swings around once a year, tipping the observer towards a different set of constellations each month CClouds of interstellar dust drift across the Solar System each year, hiding different constellations in turn DThe stars themselves complete one orbit of the Sun each year, so a different group of constellations arrives overhead during every month of the year

Question 9

Which list places the members of the Solar System in the correct order of distance from the Sun, nearest first?

AThe four rocky planets, then the asteroid belt, then the four gas giants BThe asteroid belt, then the four rocky planets, then the four gas giants CThe four gas giants, then the asteroid belt, then the four rocky planets DThe four rocky planets, then the four gas giants, then the asteroid belt

Question 10

All eight planets orbit the Sun in the same direction and in nearly the same flat plane.

What explains this?

AThe Sun’s powerful magnetic field slowly pulled all of the planets round into a single flat plane after they had first formed in random places and directions BThe planets formed within a single spinning disc of gas and dust surrounding the young Sun, so they inherited its rotation and its plane CPlanets that orbited in other directions collided with the Sun long ago, leaving only these eight survivors behind DIt is a coincidence: each planet was captured separately from interstellar space and happened to arrive similarly

Question 11

The table gives data for two planets orbiting the same star. Planet P: average orbital distance 1.0 × 10¹¹ m, orbital period 0.5 years. Planet Q: average orbital distance 4.0 × 10¹¹ m, orbital period 4.0 years.

Which conclusion follows from the data?

AP and Q move at the same speed, because orbital speed depends only on the mass of the central star BThe data must be wrong, because a planet at four times the distance must take exactly four times as long CQ travels a longer path than P but moves faster, because larger orbits always demand higher speeds DQ travels a longer path than P and also moves more slowly, which is why its period is far longer

Question 12

The average distance from the Sun to Mars is 2.3 × 10¹¹ m. The speed of light is 3.0 × 10⁸ m/s.

How long does sunlight take to reach Mars?

AAbout 8.0 minutes BAbout 1.3 seconds CAbout 13 minutes DAbout 77 minutes

Question 13

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

Which statement about its motion is correct?

AIt moves fastest when nearest the Sun, where energy transferred from its gravitational store has raised its kinetic energy most BIt moves at a constant speed throughout the whole of its orbit, because the Sun’s gravity always pulls at exactly right angles to the comet’s direction of motion CIt moves fastest when furthest from the Sun, where it has had the longest time to speed up since its last pass DIt moves fastest at the two points where its orbit crosses the orbit of the Earth, because of the Earth’s gravity

Question 14

The strength of gravity at a planet’s surface depends on the planet.

An astronaut’s MASS and WEIGHT are compared on Earth and on Mars, where the gravitational field is weaker. Which row is correct?

AMass: the same on both planets. Weight: smaller on Mars than on Earth BMass: the same on both planets. Weight: the same on both planets CMass: smaller on Mars than on Earth. Weight: smaller on Mars than on Earth DMass: smaller on Mars than on Earth. Weight: the same on both planets

Question 15

The Sun contains about 99.8% of the Solar System’s total mass.

What is the significance of this fact for the motion of the planets?

AIt explains why the planets all have the same density as the Sun, since they formed from the same material BThe Sun’s gravitational pull dominates every planet’s motion, holding the whole system in orbit around the Sun itself CIt shows that the planets must once have been part of the Sun and were thrown off by its rapid early rotation DIt means the Sun’s magnetic field is strong enough to steer the planets along their present orbital paths

Question 16

An asteroid’s orbit brings it from the asteroid belt to near the Earth’s orbit and back.

As the asteroid moves AWAY from the Sun towards the belt, what happens to its energy?

AGravitational potential energy is transferred to its kinetic store, so it speeds up steadily as it leaves the Sun BBoth its kinetic energy and its gravitational potential energy fall, because the Sun’s pull weakens with distance CKinetic energy is transferred to its gravitational potential store, so it slows down as it climbs away from the Sun DIts total energy increases, because the asteroid absorbs the sunlight that falls on it during the journey outwards

Question 17

The gas giants formed in the cold outer regions of the accretion disc, far from the young Sun.

Why was distance important for their formation?

AThe pull of the Sun’s gravity is stronger at large distances, so more material was dragged out to the outer disc BFar from the Sun it was cold enough for ices and gases to collect, giving the outer planets far more building material CSunlight pushed all of the rock in the disc outwards, leaving only gases in the inner region near the Sun DFar from the Sun the accretion disc was spinning so quickly that material was continually flung outwards and piled itself up into the giant planets there

Question 18

A planet’s year is the time it takes to complete one orbit of the Sun.

Mercury’s year is 88 Earth days, while Neptune’s year is about 165 Earth years. Which TWO factors together account for Neptune’s far longer year?

ANeptune travels at a lower speed than Mercury, although the two planets’ orbital paths are almost the same length BNeptune has a much longer orbital path than Mercury, although both planets travel at exactly the same orbital speed CNeptune has a much longer orbital path than Mercury, and it also travels along that path at a lower speed DNeptune spins more slowly on its axis than Mercury, and it is also a much more massive planet than Mercury is

Question 19

The Moon travels around the Earth in an approximately circular orbit.

What provides the force that keeps changing the Moon’s direction of travel?

AThe gravitational attraction of the Sun on the Moon, acting along the direction in which the Moon moves BThe Moon’s own engine of internal energy, which continually steers it back towards the Earth CThe gravitational attraction of the Earth on the Moon, acting towards the centre of the orbit DThere is no force acting on the Moon: objects in space continue in circles naturally without any force

Question 20

If the Earth’s gravitational pull on an orbiting satellite could be switched off instantly, what would the satellite do?

AContinue on its circular orbit at the same speed, since the orbit itself keeps the satellite turning BMove off in a straight line along the direction it was travelling at that instant, at a steady speed CSpiral slowly inwards and fall to the Earth, because its orbital speed would no longer be needed DFly radially outwards, directly away from the Earth, along the line joining it to the Earth’s centre

Question 21

The Moon orbits the Earth at an average distance of 3.8 × 10⁸ m with a period of 27 days (2.3 × 10⁶ s).

What is the Moon’s average orbital speed?

AAbout 6.1 × 10⁴ m/s BAbout 1.7 × 10² m/s CAbout 1.0 × 10³ m/s DAbout 1.0 × 10⁶ m/s

Question 22

On Mars the gravitational field strength is 3.7 N/kg. An astronaut has a mass of 60 kg.

What is the astronaut’s weight on Mars, and what would a balance calibrated in kilograms read there?

AWeight 222 N; a mass balance comparing the astronaut against standard masses would read about 23 kg BWeight 588 N; the astronaut’s weight is fixed by their body and is the same everywhere in the Universe CWeight 222 N; a mass balance comparing the astronaut against standard masses would still read 60 kg DWeight 16 N; dividing the astronaut’s mass by the field strength gives the weight on any planet

Question 23

Two satellites, R and S, are in circular orbits around the Earth. R is in a low orbit, S in a much higher one.

Which comparison of their motion is correct?

AR and S must move at identical speeds, because both of them are in free fall in the Earth’s gravitational field BR moves faster than S, but S completes each orbit in less time because its greater height assists its motion CS moves faster than R because, being further out from the Earth, it has to cover a much longer orbital path in the same fixed orbital time as R DR moves faster than S and completes each orbit in less time, because gravity is stronger at R’s smaller orbital radius

Question 24

A satellite orbits at a radius of 7.0 × 10⁶ m from the Earth’s centre, travelling at 7.5 × 10³ m/s.

What is its orbital period?

AAbout 98 minutes BAbout 26 hours CAbout 16 minutes DAbout 9.3 hours

Question 25

Which description of the Sun is correct?

AA star of exceptional size, consisting mostly of oxygen and carbon, radiating energy released by burning its fuel BA star of medium size, consisting mostly of hydrogen and helium, radiating energy released by nuclear fusion in its core CA planet large enough to glow, consisting mostly of molten rock, radiating energy stored from its original formation DA star of medium size, consisting mostly of uranium, radiating energy released by nuclear fission reactions in its core

Question 26

The Sun radiates its energy mostly in which regions of the electromagnetic spectrum?

AX-rays and gamma rays almost exclusively BVisible light only, with nothing emitted either side of it CInfrared, visible light and ultraviolet DRadio waves, microwaves and infrared only

Question 27

A main-sequence star remains stable in size for billions of years.

What balance keeps it stable?

ANothing balances: a star is a solid body like a planet and simply keeps whatever size it originally formed with BThe inward pull of its own gravity is balanced by the outward pressure produced by the fusion energy released in its core CThe inward pull of its own gravity is balanced by the outward magnetic force generated by its spinning charged core DThe inward pressure of the surrounding interstellar gas is balanced by the outward pull of the nearby stars around it

Question 28

Star A glows blue-white; star B, of similar size, glows orange-red.

What does the colour difference show?

AStar A has a hotter surface than star B BStar A has a cooler surface than star B CStar A is moving towards the Earth while star B is moving away from it DStar A is made of different chemical elements from star B

Question 29

Which sequence gives the life cycle of a star with a mass similar to the Sun’s?

ANebula → main-sequence star → protostar → white dwarf → red giant → planetary nebula BProtostar → nebula → main-sequence star → red giant → supernova → neutron star CNebula → protostar → main-sequence star → red giant → planetary nebula → white dwarf DNebula → protostar → main-sequence star → red supergiant → supernova → black hole

Question 30

A star much more massive than the Sun ends its life in a supernova explosion.

What may the collapsed core left behind become?

AA red giant, which will later shed its outer layers gently into space once more BA neutron star, or a black hole if the remaining core is massive enough CA white dwarf, or a planetary nebula if the remaining core is massive enough DA new protostar, which begins the same star’s life cycle over again from the start

Question 31

The matter in the Earth contains elements such as iron, silicon and oxygen.

According to the life cycle of stars, where were these heavy elements produced?

AInside the young Sun itself, which threw its very heaviest elements outwards into the disc while the planets were still in the process of forming around it BIn the cold gas of the original nebula, where light atoms slowly stuck together to build heavier ones over time CIn the Earth’s own core, where the enormous pressure has fused lighter atoms into iron throughout its history DInside earlier generations of stars, and scattered into space when those stars ejected material at the end of their lives

Question 32

A protostar forms at the centre of a collapsing cloud of gas and dust.

What causes its temperature to rise before fusion begins?

AFriction between the cloud and the interstellar medium heats the gas as the whole cloud drifts through space BSmall amounts of fusion happen even in the cold outer cloud, and this trickle of energy slowly warms the centre CRadiation arriving from the surrounding stars gradually warms up the entire collapsing cloud until its centre finally reaches the temperature needed for fusion DAs the cloud collapses, energy is transferred from its gravitational potential store, heating the compressed gas at the centre

Question 33

Two stars formed at the same time. Star X has a much greater mass than star Y.

Which statement about their lifetimes is correct?

ANothing can be predicted about their lifetimes, because the length of a star’s life is a random property of each individual star BX spends less time on the main sequence, because its greater core temperature makes it use up its fuel far faster than its extra mass can compensate for CX spends more time on the main sequence than Y does, because it started out with a proportionally larger store of hydrogen fuel to draw on throughout its whole lifetime DX and Y leave the main sequence together, because stars that form at the same time always evolve at exactly the same rate

Question 34

Which statement about the Milky Way is correct?

AIt is the galaxy containing the Sun, which is one of many billions of stars held together in it by gravity BIt is the name of the Solar System: the Sun, its eight planets, and the comets and asteroids that orbit it CIt is the nearest galaxy to our own, visible from the Earth as a faint band of light across the night sky DIt is a nebula inside the Solar System, lying between the orbits of the outermost planets and the nearest stars

Question 35

Distances between stars are measured in light-years.

What is one light-year?

AThe distance travelled by the Earth around the Sun in one year BThe time taken for light to cross from one side of the galaxy to the other CThe time taken for light to travel from the Sun to the Earth DThe distance travelled through space by light in one year

Question 36

One light-year is 9.5 × 10¹⁵ m. The nearest star beyond the Sun is 4.2 light-years away.

What is this distance in metres?

AAbout 1.3 × 10⁸ m BAbout 2.3 × 10¹⁵ m CAbout 4.0 × 10¹⁵ m DAbout 4.0 × 10¹⁶ m

Question 37

The light from almost every distant galaxy shows redshift.

What is redshift?

AA decrease in the observed wavelength of the light, towards the red end of the spectrum, seen when a source moves towards the observer BA change in the observed colour of a galaxy caused by clouds of red dust lying between the galaxy and the Earth CThe gradual fading of the observed brightness of a galaxy’s light as it spreads out over greater and greater distances DAn increase in the observed wavelength of the light, towards the red end of the spectrum, seen when a source moves away from the observer

Question 38

Astronomers observe that light from distant galaxies is redshifted, and that the redshift is larger for galaxies that are further away.

What conclusion is drawn from these observations?

AEvery galaxy is spinning rapidly on its axis, and the spin is fastest for the galaxies furthest away BDistant galaxies are hotter than nearby ones, and the extra heat shifts their light towards the red CThe Universe is contracting: all of the galaxies are steadily falling inwards towards the Milky Way DThe Universe is expanding: galaxies are moving apart, with the most distant ones receding the fastest

Question 39

A galaxy is receding at 1.1 × 10⁷ m/s. The Hubble constant is 2.2 × 10⁻¹⁸ per second.

Using d = v/H₀, what is the distance to the galaxy?

A5.0 × 10²⁴ m B2.0 × 10²⁴ m C2.4 × 10⁻¹¹ m D5.0 × 10²⁵ m

Question 40

The cosmic microwave background radiation (CMBR) is detected arriving almost uniformly from every direction in space.

How does the Big Bang theory account for it?

AIt is simply the combined radio output of all of the stars that are currently shining, blended together more or less evenly across the whole of the sky BIt is radiation released in the hot early Universe, which has been stretched to microwave wavelengths as the Universe expanded CIt is radiation emitted by cold clouds of dust that happen to be spread evenly around the edge of the Milky Way DIt is interference produced inside microwave detectors themselves, which no experiment has yet managed to remove

Paper 2 — Multiple Choice

Section A: The Earth, Moon and Sun

Section B: The Solar System

Section C: Orbits and Gravity

Section D: Stars

Section E: The Universe