Earth and the Solar System
Chapter 27 MCQs
Earth and the Solar System
Assume circular orbits where needed. Use π = 3.14 where needed.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
1
Which statement correctly describes the motion of the Earth?
A Earth rotates once every year and orbits the Sun once every day
B Earth rotates once every day and orbits the Sun once every year
C Earth does not rotate but orbits the Sun once every day
D Earth rotates once every month and orbits the Moon once every year
2
Which statement correctly describes the Moon?
A The Moon is a planet that orbits the Sun directly only.
B The Moon is a natural satellite of Earth.
C The Moon is a star because it gives out its own light.
D The Moon is larger than the Sun but farther away.
3
Which object provides the gravitational force that keeps Earth in orbit around the Sun?
A Moon
B Sun
C Mars
D Earth’s atmosphere
4
Which force keeps the Moon in orbit around Earth?
A magnetic force from Earth’s core
B electrostatic force between Earth and Moon
C gravitational attraction between Earth and Moon
D friction between the Moon and space
5
A planet moves in a nearly circular orbit around the Sun.
Which statement is correct?
A its velocity is constant because its speed is constant
B its velocity changes because its direction changes
C no force acts on it because it remains in orbit
D it moves in a straight line because gravity is zero in space
6
A satellite moves at constant speed in a circular orbit.
Why is it accelerating?
A its mass changes continuously
B its direction of motion changes continuously
C its speed increases continuously
D its gravitational field becomes zero
7
For a satellite in circular orbit, the gravitational force acts:
A in the direction of motion
B opposite to the direction of motion
C towards the centre of the orbit
D away from the centre of the orbit
8
A satellite is in a stable circular orbit around Earth.
What provides the centripetal force?
A friction with space
B gravitational attraction from Earth
C thrust from the satellite engine at every point
D pressure from sunlight only
9
A satellite orbits Earth at constant speed.
Which row correctly describes its speed, velocity and acceleration?
| speed | velocity | acceleration | |
|---|---|---|---|
| A | constant | constant | zero |
| B | constant | changing | towards Earth |
| C | changing | constant | away from Earth |
| D | zero | zero | towards Earth |
10
A planet is farther from the Sun than Earth.
Compared with Earth, it usually has:
A a shorter orbital period and higher orbital speed
B a longer orbital period and lower orbital speed
C the same orbital period and the same orbital speed
D no orbital period because gravity is absent
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
11
Which list shows objects in increasing average distance from the Sun?
A Mercury, Venus, Earth, Mars
B Earth, Venus, Mercury, Mars
C Mars, Earth, Venus, Mercury
D Mercury, Earth, Venus, Mars
12
Which object is not a planet?
A Jupiter
B Mars
C Moon
D Venus
13
Which object is a star?
A Earth
B Moon
C Sun
D Jupiter
14
Why does the Sun appear much brighter than other stars?
A It is the largest star in the universe.
B It is much closer to Earth than other stars.
C It reflects light from Earth.
D It is the only star that emits visible light.
15
Which statement about planets in the Solar System is correct?
A They produce their own light by nuclear fusion.
B They orbit the Sun.
C They all have the same orbital period.
D They all have the same mass and radius.
16
Which statement about asteroids is correct?
A They are small rocky bodies, many found between Mars and Jupiter.
B They are stars outside the Solar System.
C They are made only of gas and always orbit Earth.
D They are planets with nuclear fusion in their cores.
17
Which statement about comets is correct?
A They are made only of metal and travel in perfect circles.
B They often have highly elliptical orbits around the Sun.
C They are artificial satellites launched from Earth.
D They are moons of Jupiter only.
18
A comet moves closer to the Sun in its orbit.
What usually happens to its speed?
A it decreases because gravity becomes weaker
B it increases because gravitational attraction becomes stronger
C it remains exactly constant because all orbital speed is fixed
D it becomes zero at closest approach
19
A planet moves in an elliptical orbit around the Sun.
At which point is its speed greatest?
A when it is closest to the Sun
B when it is farthest from the Sun
C when it crosses Earth’s orbit only
D speed is the same at all points in an elliptical orbit
20
A satellite has an orbital radius of 7.0 × 10⁶ m and completes one orbit in 6000 s.
What is its orbital speed?
A 7.3 × 10² m/s
B 7.3 × 10³ m/s
C 4.4 × 10⁷ m/s
D 2.6 × 10¹¹ m/s
21
A planet has orbital radius 1.5 × 10¹¹ m and orbital period 3.2 × 10⁷ s.
What is its average orbital speed?
A 2.9 × 10⁴ m/s
B 4.7 × 10³ m/s
C 7.5 × 10¹⁸ m/s
D 3.0 × 10⁸ m/s
22
A moon orbits a planet at radius 4.0 × 10⁸ m with speed 1.0 × 10³ m/s.
What is its orbital period?
A 2.5 × 10³ s
B 4.0 × 10⁵ s
C 2.5 × 10⁶ s
D 2.5 × 10⁹ s
23
A satellite completes 12 orbits around Earth in 24 hours.
What is its orbital period?
A 0.50 h
B 2.0 h
C 12 h
D 288 h
24
A satellite completes one circular orbit of radius 8.0 × 10⁶ m in 100 minutes.
What is its approximate orbital speed?
A 8.4 × 10² m/s
B 8.4 × 10³ m/s
C 5.0 × 10⁷ m/s
D 8.0 × 10⁸ m/s
25
The orbital period of a satellite is doubled while its orbital radius is unchanged.
What happens to its average orbital speed?
A it doubles
B it halves
C it becomes four times larger
D it remains unchanged
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
26
Two satellites orbit Earth in circular orbits. Satellite X is closer to Earth than satellite Y.
Which statement is usually correct?
A X has a greater orbital speed and shorter period.
B X has a smaller orbital speed and longer period.
C X and Y must have the same speed.
D Y has a shorter period because it travels farther.
27
A satellite is moved to a higher circular orbit around Earth.
What happens to the gravitational field strength at the satellite?
A it increases
B it decreases
C it stays the same
D it becomes negative
28
A satellite is in orbit above Earth. Which statement is correct about its weight?
A It has zero weight because there is no gravity in orbit.
B It still has weight because Earth’s gravitational field acts on it.
C It has mass but no gravitational force acts on it.
D Its weight is caused by air resistance only.
29
Astronauts in an orbiting spacecraft appear weightless because:
A there is no gravitational force acting on them
B they and the spacecraft are falling around Earth together
C their mass becomes zero
D Earth stops attracting objects above the atmosphere
30
A satellite remains in orbit instead of falling vertically to Earth because:
A it has sideways velocity while gravity pulls it towards Earth
B gravity acts away from Earth in space
C there is no force acting on it
D the satellite is outside Earth’s gravitational field
31
A geostationary satellite orbits Earth.
Which statement is correct?
A It orbits over the poles with a period of 12 hours.
B It remains above the same point on Earth’s equator.
C It has an orbital period of one month.
D It must orbit very close to Earth’s surface.
32
Which condition is required for a geostationary satellite?
A orbit over the equator with period equal to Earth’s rotation period
B orbit over the poles with period equal to the Moon’s period
C orbit in any direction with any period
D remain fixed in space without orbiting
33
A geostationary satellite is useful for television communication because:
A it remains in a fixed position relative to the ground
B it passes over every country every 90 minutes
C it reflects sunlight only at night
D it has no gravitational force acting on it
34
A polar-orbiting satellite is often useful for mapping Earth because:
A it remains above one fixed city forever
B Earth rotates underneath it, allowing it to scan different regions
C it has no orbital motion
D it must be outside the Solar System
35
Which satellite is most suitable for continuous communication with a fixed satellite dish?
A geostationary satellite
B polar satellite
C asteroid
D the Moon only
36
Which satellite is most suitable for observing the whole Earth’s surface over time?
A geostationary satellite only
B polar-orbiting satellite
C satellite fixed above one longitude only
D satellite with zero orbital speed
37
A satellite is in a low Earth orbit and experiences slight atmospheric drag.
What happens if it loses energy and no correction is made?
A it may spiral downwards into a lower orbit
B it moves to a higher orbit automatically
C its mass becomes zero
D gravity stops acting on it
38
Why do satellites in very low orbits need occasional boosts?
A to replace energy lost due to atmospheric drag
B to remove all gravitational force
C to make their mass larger
D to stop Earth rotating
39
A satellite moves in a circular orbit. If the gravitational force suddenly disappeared, what would the satellite do?
A continue in a straight line tangent to the orbit
B move instantly towards Earth
C continue in the same circular orbit
D stop immediately
40
A planet moves around the Sun in a stable orbit.
Which statement best explains why it does not move in a straight line?
A The Sun’s gravitational force continuously changes its direction of motion.
B Space friction pushes it sideways.
C The planet has no inertia.
D The planet is attached to the Sun by magnetic field lines.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
41
Earth’s gravitational field strength at its surface is about 10 N/kg.
A satellite of mass 500 kg is at a point where gravitational field strength is 2.0 N/kg.
What is the gravitational force on the satellite?
A 0.0040 N
B 250 N
C 1000 N
D 2500 N
42
At a point in space, gravitational field strength due to Earth is 0.40 N/kg.
What force acts on a 200 kg spacecraft at that point?
A 0.0020 N
B 80 N
C 500 N
D 2000 N
43
An object has mass 60 kg. On the Moon, gravitational field strength is about 1.6 N/kg.
What is its weight on the Moon?
A 37.5 N
B 60 N
C 96 N
D 600 N
44
A person’s weight on Earth is 720 N. Earth’s gravitational field strength is 10 N/kg.
What is the person’s mass?
A 7.2 kg
B 72 kg
C 720 kg
D 7200 kg
45
A spacecraft travels from Earth to the Moon.
Which quantity remains constant for the spacecraft?
A mass
B weight
C gravitational force from Earth
D gravitational field strength around it
46
A satellite moves from a low orbit to a much higher orbit.
Which row is correct?
| gravitational field strength | orbital period | |
|---|---|---|
| A | decreases | increases |
| B | decreases | decreases |
| C | increases | increases |
| D | increases | decreases |
47
Which statement about gravitational fields is correct?
A gravitational forces are always repulsive
B gravitational field strength decreases with distance from the mass
C gravity acts only where there is air
D gravity acts only on magnetic materials
48
An object is taken from Earth’s surface to a point far from Earth.
What happens to its mass and weight?
| mass | weight | |
|---|---|---|
| A | decreases | decreases |
| B | unchanged | decreases |
| C | unchanged | unchanged |
| D | increases | decreases |
49
Why do planets orbit the Sun rather than the Earth?
A the Sun contains most of the mass of the Solar System and exerts the dominant gravitational attraction
B Earth has no gravity
C planets are magnetic and Earth is not
D planets are pushed around by light from Earth
50
Which statement best describes the Solar System?
A the Sun and the objects gravitationally bound to it
B Earth and the Moon only
C all galaxies in the universe
D only the eight planets, not including the Sun
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
Chapter 27 Answer Key
Earth and the Solar System
| Q | Ans | Q | Ans | Q | Ans | Q | Ans | Q | Ans |
|---|---|---|---|---|---|---|---|---|---|
| 1 | B | 11 | A | 21 | A | 31 | B | 41 | C |
| 2 | B | 12 | C | 22 | C | 32 | A | 42 | B |
| 3 | B | 13 | C | 23 | B | 33 | A | 43 | C |
| 4 | C | 14 | B | 24 | B | 34 | B | 44 | B |
| 5 | B | 15 | B | 25 | B | 35 | A | 45 | A |
| 6 | B | 16 | A | 26 | A | 36 | B | 46 | A |
| 7 | C | 17 | B | 27 | B | 37 | A | 47 | B |
| 8 | B | 18 | B | 28 | B | 38 | A | 48 | B |
| 9 | B | 19 | A | 29 | B | 39 | A | 49 | A |
| 10 | B | 20 | B | 30 | A | 40 | A | 50 | A |
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
Detailed Explanations
1. B
-
Earth rotates once about its axis in about one day.
-
Earth orbits the Sun once in about one year.
-
Rotation gives day and night.
-
Revolution around the Sun gives the year.
2. B
-
The Moon is a natural satellite of Earth.
-
It orbits Earth.
-
It does not produce its own light; it reflects sunlight.
3. B
-
The Sun’s gravitational attraction provides the centripetal force for Earth’s orbit.
-
Without this force, Earth would move off in a straight line.
4. C
-
The Moon is kept in orbit by gravitational attraction between Earth and the Moon.
-
There is no frictional force in space keeping it in orbit.
5. B
-
Velocity includes both speed and direction.
-
In circular motion, the direction changes continuously.
-
So even if speed is constant, velocity changes.
6. B
-
Acceleration means change in velocity.
-
In circular motion, the direction of velocity changes continuously.
-
Therefore the satellite accelerates even if its speed is constant.
7. C
-
In circular orbit, the centripetal force acts towards the centre of the orbit.
-
For planets/satellites, this force is gravitational force.
8. B
-
Earth’s gravitational attraction provides the centripetal force for an orbiting satellite.
-
The satellite does not need continuous engine thrust in a stable orbit.
9. B
-
Speed can be constant in circular orbit.
-
Velocity changes because direction changes.
-
Acceleration is towards Earth, the centre of the orbit.
10. B
-
Planets farther from the Sun usually move more slowly.
-
They also take longer to complete one orbit.
-
So orbital period is longer and orbital speed is lower.
11. A
-
Correct order from the Sun:
-
Mercury
-
Venus
-
Earth
-
Mars
-
12. C
-
The Moon is not a planet.
-
It is a natural satellite of Earth.
13. C
-
The Sun is a star.
-
It produces its own energy by nuclear fusion.
14. B
-
The Sun appears much brighter than other stars because it is much closer to Earth.
-
Other stars may be very bright, but they are extremely far away.
15. B
-
Planets orbit the Sun.
-
They do not produce their own light by nuclear fusion.
-
They reflect light from the Sun.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
16. A
-
Asteroids are small rocky bodies.
-
Many are found in the asteroid belt between Mars and Jupiter.
17. B
-
Comets often have highly elliptical orbits around the Sun.
-
They are made of ice, dust and rocky material.
18. B
-
As a comet moves closer to the Sun, gravitational attraction becomes stronger.
-
The comet speeds up.
-
Closest to the Sun, it usually has greatest speed.
19. A
-
In an elliptical orbit, speed is greatest when the object is closest to the Sun.
-
Speed is lowest when it is farthest from the Sun.
20. B
-
Orbital speed = circumference / time.
-
Circumference = 2πr.
-
v = 2 × 3.14 × 7.0 × 10⁶ / 6000
-
v = 4.396 × 10⁷ / 6000
-
v ≈ 7.3 × 10³ m/s
21. A
-
v = 2πr / T
-
v = 2 × 3.14 × 1.5 × 10¹¹ / 3.2 × 10⁷
-
v = 9.42 × 10¹¹ / 3.2 × 10⁷
-
v ≈ 2.9 × 10⁴ m/s
22. C
-
Orbital period = circumference / speed.
-
T = 2πr / v
-
T = 2 × 3.14 × 4.0 × 10⁸ / 1.0 × 10³
-
T = 2.512 × 10⁹ / 10³
-
T = 2.5 × 10⁶ s
23. B
-
12 orbits are completed in 24 hours.
-
Time for 1 orbit = 24 / 12
-
Time for 1 orbit = 2.0 h
24. B
-
Time = 100 minutes = 6000 s.
-
v = 2πr / T
-
v = 2 × 3.14 × 8.0 × 10⁶ / 6000
-
v = 5.024 × 10⁷ / 6000
-
v ≈ 8.4 × 10³ m/s
25. B
-
Orbital speed = circumference / period.
-
If orbital radius is unchanged, circumference is unchanged.
-
If period doubles, speed halves.
26. A
-
A satellite closer to Earth usually has:
-
greater orbital speed
-
shorter orbital period
-
-
A higher orbit has lower speed and longer period.
27. B
-
Gravitational field strength decreases as distance from Earth increases.
-
So a higher orbit has weaker gravitational field strength.
28. B
-
A satellite in orbit is still in Earth’s gravitational field.
-
Therefore it still has weight.
-
It is not true that gravity is zero in orbit.
29. B
-
Astronauts appear weightless because they and the spacecraft are falling around Earth together.
-
They are in continuous free fall.
-
Gravity still acts on them.
30. A
-
A satellite has sideways velocity.
-
Gravity pulls it towards Earth.
-
The combination makes it fall around Earth rather than straight down.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
31. B
-
A geostationary satellite remains above the same point on Earth’s equator.
-
It has the same angular speed as Earth’s rotation.
32. A
-
A geostationary satellite must:
-
orbit above the equator
-
move in the same direction as Earth’s rotation
-
have period equal to Earth’s rotation period
-
33. A
-
Since it appears fixed above one point, a ground satellite dish can point at it continuously.
-
This makes it useful for communication and TV broadcasting.
34. B
-
A polar satellite passes over the poles.
-
Earth rotates beneath it.
-
Over time, it can scan many different regions of Earth.
35. A
-
Continuous communication with a fixed dish needs a satellite that stays in the same position in the sky.
-
That is a geostationary satellite.
36. B
-
A polar-orbiting satellite is suitable for observing the whole Earth over time.
-
Earth rotates underneath its path.
37. A
-
Atmospheric drag removes energy from a low-orbit satellite.
-
If no correction is made, it may spiral downwards into a lower orbit.
-
Eventually, it may re-enter the atmosphere.
38. A
-
Low-orbit satellites experience slight atmospheric drag.
-
Boosts replace lost energy and maintain the orbit.
39. A
-
If gravitational force disappeared, there would be no centripetal force.
-
The satellite would continue in a straight line tangent to the orbit.
-
That is Newton trying to leave the group chat.
40. A
-
The Sun’s gravity continuously changes the planet’s direction of motion.
-
This prevents the planet from moving in a straight line.
41. C
-
Weight/gravitational force = mass × gravitational field strength.
-
F = mg
-
F = 500 × 2.0
-
F = 1000 N
42. B
-
F = mg
-
F = 200 × 0.40
-
F = 80 N
43. C
-
Weight = mass × gravitational field strength.
-
W = mg
-
W = 60 × 1.6
-
W = 96 N
44. B
-
Weight = mass × gravitational field strength.
-
m = W / g
-
m = 720 / 10
-
m = 72 kg
45. A
-
Mass remains constant wherever the spacecraft goes.
-
Weight changes because gravitational field strength changes.
-
Mass is the amount of matter; weight is gravitational force.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
46. A
-
In a higher orbit:
-
gravitational field strength decreases
-
orbital period increases
-
-
Higher satellites take longer to complete an orbit.
47. B
-
Gravitational field strength decreases with distance from the mass.
-
Gravity is attractive, not repulsive.
-
Gravity does not need air.
48. B
-
Mass remains unchanged.
-
Weight decreases because gravitational field strength decreases farther from Earth.
49. A
-
The Sun contains most of the mass of the Solar System.
-
Its gravitational attraction dominates the motion of planets.
-
Therefore planets orbit the Sun.
50. A
-
The Solar System is the Sun and all objects gravitationally bound to it.
-
This includes planets, dwarf planets, moons, asteroids, comets and other smaller bodies.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
Common Traps From This Chapter
| Trap | Correct Rule |
|---|---|
| Earth rotation | once per day |
| Earth orbit | once per year |
| Moon | natural satellite of Earth |
| Sun | star, source of light |
| Planets | orbit the Sun and reflect light |
| Orbiting object | has changing velocity |
| Circular motion | acceleration towards centre |
| Centripetal force in orbit | gravity |
| Constant speed orbit | velocity still changes |
| Farther planet | longer period, lower speed |
| Orbital speed | v = 2πr/T |
| Orbital period | T = 2πr/v |
| Satellite in orbit | still has weight |
| Astronaut “weightlessness” | free fall around Earth |
| Stable orbit | sideways velocity + gravity |
| Geostationary satellite | equator, same period as Earth rotation |
| Polar satellite | scans Earth as Earth rotates beneath |
| Low orbit drag | causes energy loss |
| If gravity vanished | object moves tangent in straight line |
| Weight | W = mg |
| Mass | unchanged with location |
| Weight | changes with gravitational field strength |
| Higher orbit | weaker g, longer period |
| Gravity | attractive and acts through space |
| Solar System | Sun plus objects bound by its gravity |