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

Question 1

A geostationary satellite orbits Earth at a radius of 42 200 km from the centre. Its orbital period is exactly 24 hours (86 400 s).

What is its orbital speed?

A1.8 km/s B3.1 km/s C4.9 km/s D7.9 km/s

Question 2

At the December solstice, an observer at Greenwich would notice that the Sun:

ARises due east and sets due west BRises in the northeast and sets in the northwest CRises in the southeast and sets in the southwest DDoes not rise at all

Question 3

The Moon’s orbital period is 27.3 days, but the time between successive full Moons is 29.5 days. The difference is because:

AThe Moon speeds up and slows down during its orbit BEarth has moved along its own orbit, so the Moon must travel a bit further to reach the same Sun-Earth-Moon alignment CThe Moon’s orbit is not circular DEarth’s rotation slows down the apparent motion of the Moon

Question 4

A satellite in a circular orbit has its orbital radius doubled. How does its orbital speed change?

(Assume the period increases as the radius increases.)

AThe speed doubles BThe speed halves CThe speed decreases but does not halve DThe speed remains the same

Question 5

During a lunar eclipse observed from the UK, the Moon passes through:

AThe Sun’s shadow BThe Earth’s shadow CIts own shadow DJupiter’s shadow

Question 6

If the Earth’s axis had zero tilt (were perpendicular to the orbital plane), what would happen to the seasons?

ASeasons would become more extreme BThere would be no seasonal variation in temperature COnly the poles would experience seasons DThe length of a year would change

Question 7

A low-Earth orbit satellite has an orbital speed of 7.8 km/s and a period of 5500 s. What is its orbital radius?

A4300 km B6800 km C8600 km D13 600 km

Question 8

A student claims that Venus is hotter than Mercury despite being further from the Sun. Which explanation is correct?

AVenus is larger so contains more internal heat BVenus has a dense CO₂ atmosphere that traps heat by the greenhouse effect CVenus orbits the Sun faster than Mercury DVenus is closer to Earth and receives reflected heat

Question 9

Neptune is approximately 4.5 × 10¹² m from the Sun. How long does light take to travel from the Sun to Neptune?

(Speed of light c = 3.0 × 10⁸ m/s)

A1.5 × 10⁴ s (about 4 hours) B1.5 × 10³ s (about 25 minutes) C1.5 × 10⁵ s (about 42 hours) D1.5 × 10² s (about 2.5 minutes)

Question 10

The ESA JUICE mission is travelling to Jupiter’s icy moons. Jupiter’s orbital radius is 7.8 × 10¹¹ m and its orbital period is 3.74 × 10⁸ s.

What is Jupiter’s orbital speed around the Sun?

A6.6 × 10³ m/s B1.3 × 10⁴ m/s C2.6 × 10⁴ m/s D3.0 × 10⁴ m/s

Question 11

Planet X has a surface gravitational field strength of 25 N/kg and Planet Y has 4.0 N/kg. An object weighs 500 N on Planet X.

What does it weigh on Planet Y?

A20 N B80 N C500 N D3125 N

Question 12

In the early Solar System, which process allowed small dust grains to grow into kilometre-sized planetesimals?

ANuclear fusion BGravitational accretion — small particles collided, stuck together, and grew CElectromagnetic radiation from the Sun melted them together DChemical reactions in space converted gas directly into rock

Question 13

A planet orbits a star in an elliptical path. At its closest point (perihelion) it is 1.0 × 10¹¹ m from the star and at its farthest point (aphelion) it is 3.0 × 10¹¹ m.

If its speed at perihelion is 45 km/s, which statement about its speed at aphelion is correct?

AIt is exactly 45 km/s (speed is constant) BIt is greater than 45 km/s CIt is less than 45 km/s DIt is exactly 15 km/s

Question 14

Saturn is approximately 1.4 × 10¹² m from the Sun and has an orbital period of 9.3 × 10⁸ s. Mars is 2.3 × 10¹¹ m from the Sun with a period of 5.9 × 10⁷ s.

Which planet has the greater orbital speed?

ASaturn, because it has a larger orbit BMars, because it is closer to the Sun CThey have the same orbital speed DSaturn, because it has more mass

Question 15

Two asteroids orbit the Sun. Asteroid A is at twice the distance of Asteroid B. Which statement is correct?

AAsteroid A has a shorter orbital period and higher speed BAsteroid A has a longer orbital period and lower speed CAsteroid A has a longer orbital period and higher speed DBoth have the same period and speed

Question 16

During the formation of the Solar System, why did the inner planets form as rocky bodies while the outer planets formed as gas giants?

AThe inner planets formed first and used up all the gas BCloser to the Sun, temperatures were too high for gases to condense, so only rock and metal remained; further out, it was cold enough for ices and gases to accumulate CThe outer planets captured gas from passing comets DRocky material is heavier and sank towards the Sun

Question 17

In the Sun’s core, hydrogen nuclei fuse to form helium. Approximately what percentage of the hydrogen mass is converted to energy in this process?

AAbout 0.7% BAbout 7% CAbout 50% DAbout 100%

Question 18

The Sun’s surface temperature is about 5500°C. If you were to measure the peak wavelength of the Sun’s emission, in which part of the electromagnetic spectrum would it fall?

AUltraviolet BVisible light (yellow-green) CInfrared DRadio waves

Question 19

A student says “The Sun burns hydrogen like a gas fire.”

Why is this statement incorrect?

AThe Sun uses helium, not hydrogen BThe Sun’s process is nuclear fusion, not chemical combustion; nuclei combine rather than atoms reacting with oxygen CThe Sun is too hot for burning to occur DHydrogen cannot burn

Question 20

ESA’s Solar Orbiter mission studies the Sun from close range. Which statement about the Sun’s energy production is correct?

AFusion occurs throughout the entire Sun BFusion occurs only in the core where temperature and pressure are high enough CFusion occurs mainly at the Sun’s surface DThe Sun produces energy by gravitational contraction only

Question 21

The Sun will eventually leave the main sequence. What will happen to it?

AIt will explode as a supernova immediately BIt will expand into a red giant, then shed outer layers to become a white dwarf CIt will collapse directly into a black hole DIt will become a neutron star

Question 22

Two stars have the same surface temperature. Star P is 100 times more luminous than Star Q.

What can be concluded?

AStar P must be much larger than Star Q BStar P must be much closer than Star Q CStar Q must be hotter than Star P DBoth stars must be the same size

Question 23

A protostar becomes a main sequence star when:

AIt starts to rotate BIts core temperature becomes high enough for hydrogen fusion to begin CIt begins to emit visible light DIt attracts enough dust to form planets

Question 24

Astronomers at Jodrell Bank detect radio signals from a rapidly spinning neutron star (pulsar). This neutron star could NOT have formed from:

AA star originally 20 times the mass of the Sun BA star originally 10 times the mass of the Sun CA star originally the same mass as the Sun DA star originally 8 times the mass of the Sun

Question 25

A galaxy observed by the Royal Astronomical Society is 2.0 × 10²² m away. Express this distance in light-years.

(1 ly = 9.5 × 10¹⁵ m)

A210 ly B2100 ly C21 000 ly D210 000 ly

Question 26

Which sequence correctly orders stellar objects from largest to smallest physical size?

ARed supergiant, main sequence star, white dwarf, neutron star BNeutron star, white dwarf, main sequence star, red supergiant CWhite dwarf, neutron star, main sequence star, red supergiant DMain sequence star, red supergiant, neutron star, white dwarf

Question 27

A star has a life span of 10 billion years on the main sequence. A star 10 times more massive would have a main sequence lifetime of approximately:

A100 billion years B10 billion years C1 billion years D100 million years

Question 28

During a supernova, elements heavier than iron are created. Why can’t these elements form by normal stellar fusion?

AHeavy elements are too large to fit inside a star BFusing nuclei heavier than iron requires energy input rather than releasing energy, so it cannot sustain the star CIron does not exist inside stars DThe temperature inside stars is too low

Question 29

The Crab Nebula, observed through the Lovell Telescope at Jodrell Bank, is a supernova remnant about 6500 light-years away.

How far is this in metres? (1 ly = 9.5 × 10¹⁵ m)

A6.2 × 10¹⁹ m B6.2 × 10²⁰ m C6.2 × 10¹⁸ m D6.2 × 10²¹ m

Question 30

A white dwarf has a mass similar to the Sun but a radius similar to Earth. Compared to the Sun, the white dwarf’s surface gravitational field strength is:

AMuch weaker BAbout the same CMuch stronger DZero, because it has no fusion

Question 31

Galaxy A is 5.0 × 10²⁴ m away with a recession velocity of 1.1 × 10⁷ m/s. Galaxy B is 2.5 × 10²⁴ m away.

Using Hubble’s law, what is Galaxy B’s recession velocity?

A2.2 × 10⁷ m/s B1.1 × 10⁷ m/s C5.5 × 10⁶ m/s D2.75 × 10⁶ m/s

Question 32

A student observes a galaxy whose light has been redshifted so that a spectral line normally at 500 nm appears at 510 nm. This means the galaxy is:

AMoving towards us, because the wavelength has increased BMoving away from us, because the wavelength has increased CMoving towards us, because the wavelength has decreased DStationary, because the change is small

Question 33

The cosmic microwave background radiation is important evidence for the Big Bang because:

AIt shows that the Universe is contracting BIt is the predicted cooled remnant of the extremely hot radiation from the early Universe CIt proves that all galaxies are the same age DIt shows that the Universe has always been the same temperature

Question 34

The Hubble constant is measured as 2.2 × 10⁻¹⁸ s⁻¹.

How old is the Universe in years? (1 year ≈ 3.15 × 10⁷ s)

A7.0 × 10⁹ years B1.4 × 10¹⁰ years C2.8 × 10¹⁰ years D4.5 × 10¹⁷ years

Question 35

If the Hubble constant were found to be larger than currently estimated, the estimated age of the Universe would:

AIncrease, because the Universe would be expanding faster BDecrease, because age = 1/H₀ CStay the same, because H₀ does not affect age DBecome infinite

Question 36

Two galaxies, P and Q, are observed from Earth. P has a redshift 3 times greater than Q. Galaxy Q is 1.5 × 10²⁴ m from Earth.

How far away is Galaxy P?

A0.5 × 10²⁴ m B1.5 × 10²⁴ m C3.0 × 10²⁴ m D4.5 × 10²⁴ m

Question 37

A galaxy is 3.0 × 10²⁴ m away and has a recession velocity of 6.6 × 10⁶ m/s.

How long would it take light to travel from this galaxy to Earth? (1 year ≈ 3.15 × 10⁷ s)

A1.0 × 10⁸ years B1.0 × 10⁹ years C3.2 × 10⁸ years D3.2 × 10⁹ years

Question 38

The expansion of the Universe means that:

AGalaxies are moving through space away from a central point BSpace itself is expanding, carrying galaxies with it — there is no centre COnly distant galaxies are affected; nearby galaxies are stationary DThe galaxies are getting larger

Question 39

A student calculates the age of the Universe using two different galaxies and gets slightly different values of H₀. This is most likely because:

AThe Big Bang theory is wrong BHubble’s law is exact and should give identical results CMeasurement uncertainties in galaxy distances and velocities lead to slightly different calculated values DDifferent galaxies have different values of H₀

Question 40

If the Universe has been expanding since the Big Bang, and we observe CMBR at a temperature of 2.7 K today, what can we conclude about the Universe at the time the CMBR was emitted?

AIt was at a similar temperature to today BIt was much hotter, and the radiation has been stretched to longer wavelengths as the Universe expanded CIt was much cooler, and the radiation has been compressed DThe temperature of the CMBR has remained constant

Paper 2 — Multiple Choice

Section A: The Earth

Section B: The Solar System

Section C: The Sun as a Star

Section D: Stars

Section E: The Universe