3.3 Man Made Satellites

MODUL PDP SPM
PASCA PKP
NEGERI PERAK
2020

PHYSICS Form 4

3.3:
Man-made
Satellites

0

3.3 Man-made Satellites

Learning Standard:

Pupils are able to:

• describe how an orbit of a satellite is maintained at a specific height by setting the
necessary satellite’s velocity.

• communicate on geostationary and non-geostationary satellites.
• conceptualize escape velocity.
• solve problems involving the escape velocity, v for a rocket from the Earth’s surface,

the Moon’s surface, Mars’ surface and the Sun’s surface.

1

notE

Introduction to ISS (International Space Station)
 Diagram 1 shows International Space Station, ISS which a project that involved 15
countries including NASA (United States), Roscosmos (Russia), European Space Agency
(Europe), Japanese Aerospace Exploration Agency (Japan) and Canadian Space Agency
(Canada).

Diagram 1: International Space Station, ISS
 ISS was first built in between 1998 and 2011. ISS was occupied by astronauts since

year 2000 until now. Diagram 2 shows astronauts that live in ISS.

Diagram 2: Life of astronauts in ISS
 Astronauts that stay in ISS use most of time to conduct experiments, repair stations

and go on spacewalks.
 ISS can be seen from the Earth because of its large size.

2

 ISS orbits the Earth at a height of 408 km in 90 minutes at the linear speed of ≈
28000 /ℎ. In other words, the distance that is travelled by ISS everyday = the

distance travelled from the Earth to the Moon and back to the Earth.
 The position and path of ISS can be identified via ‘https://spotthestation.nasa.gov/’ as

shown in Diagram 3, which the date, time and time interval ISS can be spotted in the

sky at the location selected.

Diagram 3: The position of ISS from your location, for example, Ipoh, Malaysia.

 Diagram 4 shows ISS is seen in this 30 second exposure as it flies over Elkton in United
Stated on 1st August 2015.

Diagram 4: ISS is seen in the sky

3

 Diagram 5 shows MEASAT-3 satellite (Malaysia-East Asia Satellite), which is the
communication satellite for Malaysia.

Diagram 5: MEASAT 3
 Malaysia has three communication satellites, they are MEASAT-1, MEASAT-2 dan

MEASAT-3.
All three satellites are small-sized geostationary satellites, orbiting at the height of
35786 km (in different angles) with certain linear speeds and cannot be seen from the
Earth.
Orbit of Satellite:
1. Derivation of formula for linear speed of satellite, :

Diagram 6: Orbit of a satellite

Gravitational

Centripetal = force between
force,
satellite and the

2 Earth, F

= =
2
2 = 2
2 ×

2 =

2 = × 1


, = �

4

2. Diagram 7 shows a satellite at height, h from the surface of the Earth. As GM is
constant, linear speed of the satellite only depends on the radius of its orbit.

Radius of its orbit, = + ℎ
= radius of the Earth + height of the satellite

above the surface of the Earth

Thus, linear speed of the satellite, at the height, ℎ

, = � Substitute = +

= � +

Diagram 7: A satellite at height, h from the surface of the Earth

3. Example of calculation of linear speed, v for a satellite:

= 20200 km Linear speed, for a Global Positioning System (GPS)
satellite at the height, h

ℎ = 20200
= 20 200 × 1000
= 2.02 × 107

, = + ℎ
= (6.37 × 106) + (2.02 × 107)
= 2.657 × 107

, = �

, = �(6.67 × 10−11) × (5.97 × 1024)
= 6.67 × 10−11 2 −2 2.657 × 107
ℎ ℎ,
= 3.87 × 103 −1
= 5.97 × 1024

5

4. Every orbit has certain required value of linear speed that remains the satellite
orbiting the earth.
Diagram 8 and 9 shows the conditions of a satellite at a high enough linear speed and
a lower linear speed than the required.
Satellite moves with a high enough linear speed
, Linear speed = �

Centripetal acceleration
= gravitational acceleration

Satellite moves in a circular orbit around the Earth
Diagram 8: Condition of satellite at a high enough linear speed

5.
Satellite moves with a lower linear speed than the required

Satellite will < 1 Satellite will fall
enter the to a lower orbit

atmosphere &
and get burned. continue to
(air resistance
revolve
& high linear towards the
speed) Earth until it
enters the
atmosphere.

Diagram 9: Condition of satellite at a lower linear speed than the required
6

Geostationary and Non-Geostationary Satellites:
1. Diagram 10 shows the comparison between geostationary and non-geostationary
satellites.

Diagram 10: Comparison between geostationary and non-geostationary satellites

Escape velocity:
1. Escape velocity, v:
The minimum velocity needed by an object on the surface of the Earth to overcome
the gravitational force and escape to outer space.

2. Diagram 11 shows an object launched at escape velocity, . The object can overcome
the gravitational force and move an infinite distance from the Earth.

Diagram 11: Object launched at escape velocity

7

3. Escape velocity is achieved when the minimum kinetic energy, = 1 2 of an
2
object is able to overcome its gravitational potential energy, = − .

Minimum kinetic energy + Gravitational potential energy = 0

1 2 + �− � = 0
2

1 2 =
2

2 = ×2


2 = 2 1
×

2 = 2


= �2 Mass of the Earth

Distance of the object from the
centre of the Earth

If the object is on the surface of the
Earth, = (radius of the Earth)

6. According to the formula of escape velocity shown, escape velocity, depends on
(i) (mass of the Earth) dan
(ii) (distance of the object from the centre of the Earth),
(iii) DOES NOT depends on mass of the object, m that is released to the outer
space.

7. Escape velocity from the Earth,

8

11.2 −1 = 11200 −1
= 40300 −1

As the Earth has a large mass, escape velocity from
the Earth also has a high value.

8. Benefits and implications of escape velocity :
(i) Able to maintain a layer of atmosphere on the Earth, air molecules will not
escape from the Earth.
o Average linear speed of air molecules 500 −1 < escape velocity
from the Earth 11200 −1
(ii) Enable commercial aircrafts or fighter jets to fly high in the atmosphere, will
not escape to the outer space.
o Supersonic linear speed of fighter jet 2200 −1 < escape velocity
from the Earth 11200 −1
o Linear speed of commercial aircraft 250 −1 < escape velocity from
the Earth 11200 −1
(iii) The launching of rockets
o The combustion of large quantities of fuel will produce a high thrust
enables the rocket to achieve escape velocity of the Earth in order to
send the spacecraft into outer space.

9. The escape velocity is different in each planet depending on the mass of the planet.
• The escape velocity of Mars is low, therefore the atmosphere on Mars is 100
times less dense than Earth’s atmosphere.
• Jupiter has a high escape velocity, thus the hot gases on its surface cannot
escape into outer space.

9

MIND MAP

10

FAQ

No Question And Answer
1 Q How do orbits work???

A An orbit is the curved path of an object, such as a satellite, around a planet,
moon or star. It is balance between moving forwards and falling downwards.
In space, an object tends to go straight on unless a force affects it.

Click this link : https://www.youtube.com/watch?v=MkbUzfTq3w4

2 Q What is a man-made satellite?

A A satellite is an object that revolves around another object. In space,
satellites may be natural, like our moon, or planets like mars. If a satellite is
man-made, then it was built on earth and then launched into space.
Weather satellites are an example of a man-made satellite. Man-made
satellites that send back pictures and useful scientific information have
explored many of our planets in our solar system.

3 Q Why is gravitational potential energy zero at infinity?

A We place the zero point of gravitational potential energy at a distance r of
infinity. This makes all values of the gravitational potential energy negative.
It turns out that it makes sense to do this because as the distance r becomes
large, the gravitational force tends rapidly towards zero.

4 Q What is non geostationary satellite?

A Very generally speaking, there are 3 type of orbits, where you can position
satellites:
• Geostationary Orbit, about 36,000 Km above the Earth
• Mid Earth Orbit (MEO), about 8000 Km above the Earth
• Low Earth Orbit, from 160 to 2000 Km above the Earth.
So a non-geostationary satellite is one that is not positioned in a
Geostationary orbit. Of course, the Orbit in which the satellite is located also
will dictate the application for the satellite. It’s used to get the information
for weather broadcasting, GPS and imaging the earth surface.

11

5 Q What is the average lifespan of a satellite?

The average life span of a LEO satellite is approximately 5 years, but the average life
A span for a GEO satellite is approximately 8 years.

6 Q What is the time period of geostationary satellite?

23 hours and 56 minutes. Geostationary orbit, a circular orbit 35,785 km
A (22,236 miles) above Earth's Equator in which a satellite's orbital period is

equal to Earth's rotation period of 23 hours and 56 minutes. A spacecraft in
this orbit appears to an observer on Earth to be stationary in the sky

Kindly click to this link and see the video
https://www.youtube.com/watch?v=XzhVK09YReA

7 Q What is geostationary satellite and its uses?

An artificial satellite which revolves around the Earth in stable circular orbit
A in equatorial plane, having same direction and period of revolution as that of

the rotation of the Earth about it's own axis is known as geostationary
satellite. Uses: To send radio and TV signals from one place to long distance

8 Q What is the most important application of geostationary satellite?

A Meteorology. A worldwide network of operational geostationary meteorological
satellites is used to provide visible and infrared images of Earth's surface and
atmosphere for weather observation, oceanography, and atmospheric tracking. As
of 2019 there are 19 satellites in either operation or stand-by.

9Q

A

If you could launch a spacecraft
into the air, Earth’s pull of gravity
would soon bring it back down.
The harder you launch it, the
higher it goes but it would never
reach very far. At Earth’s surface
this means a speed of 11
kilometres per second, which is
known as the escape velocity.

Source: How its work?? Space Exploration By Steve Parker; Grolier(2010).

12

EXERCISE 3.3

SECTION A

1 A satellite orbiting Earth with a linear orbital speed.
Which of the following physical quantities does not affect linear speed of a
satellite?
[Mengetahui]
A Mass of Earth
B Mass of satellite
C Gravitational constant
D Radius of orbit

2 What is the linear orbital speed of the moon revolve around Earth?

[G = 6.7 x 10-11 Nm2 kg-2 , Mass of Earth= 6 x 1024 kg [Mengaplikasi kuantitatif]
Distance moon from Earth = 6.5 x106 m]

A 61842496 m s-1
B 120185 m s-1
C 7864 m s-1
D 1174 m s-1

3 Diagram 1 shows orbit of a rocket along curve R when it moves with linear speed v.

Diagram1
If the speed suddenly decreases to − 1 v , which is the new orbit for the rocket?

2
[Memahami]

13

AP
BQ
CS
DT

4 The escape velocity is
[Mengetahui]

A the minimum velocity required by an object on the surface of the earth to
overcome the gravitational force and moves around the Earth

B the minimum velocity required by an object on the surface of the earth to
overcome the gravitational force and escape into outer space.

C the maximum velocity required by an object on the surface of the earth to
overcome the gravitational force and escape into outer space

D the maximum velocity required by an object on the surface of the earth to
overcome the gravitational force and moves around the Earth

5 Statement below are differentiate between Geostationary and Non-geostationary

satellites except

[Menilai]

Geostationary satellite Non-geostationary satellites

A Orbit period is 24 hours, same to the Orbit period can be more than or less

earth orbit period. than 24 hours.

B Direction of rotation is the same as Direction of rotation must not be the
direction of rotation of the Earth. same as direction of rotation of the
Earth.

C It is always seen to be stationary by It is always seen to be changing

an observer at the surface of the position by an observer at the

Earth . surface of the Earth .

D It is used to get the information for It is used to communicate throughout
weather broadcasting, GPS and the whole world .
imaging the earth surface

14

SECTION B
6. Diagram shows a satellite Z is orbiting the earth.

Satellite Z

a) State one factor affecting linear speed of a satellite

[mengetahui]

…………………………………………………………………………………………………………………………….

b) State the relationship between linear speed and radius of orbit [ Memahami ]

…………………………………………………………………………………………………………………………….
c) Explain what will happen to the satellite if a satellite moves around the earth

with a speed which is lower than the answer in (c)
[Memahami]

…………………………………………………………………………………………………………………………….

…………………………………………………………………………………………………………………………….

…………………………………………………………………………………………………………………………….

…………………………………………………………………………………………………………………………….

7. Mercury and Venus are planets in our Solar System. The acceleration due to gravity and
the escape velocity in both planets are different. Table 1 shows the mass and radius of
both planets.

Planet Mass, m/kg Radius, r/m
Mercury 3.30 x 1023 2.44 x 106
Venus 6.42 x 1024 3.40 x 106

Table 1

15

Given Gravitational constant, G = 6.67 x10-11 N m2 kg–2,

(a) From the table 1, calculate : [Mengaplikasi kuantitatif]

(i) Acceleration due to gravity at Mercury and Venus.

(ii) Escape velocity at Mercury and Venus

(b) Compare the value of acceleration due to gravity and escape velocity at both

planets. [Memahami]

…………………………………………………………………………………………………………………………….

(c ) Explain your answer in 1(b). [Memahami]

…………………………………………………………………………………………………………………………….

16

TITLE : 3.3 MANMADE SATELLITES

Title link QR CODE
MAN-MADE SATELLITES https://youtu.be/63NcjfZ1e60

ARTIFICIAL SATELLITES OF EARTH https://youtu.be/bA-V2DixZBk
AND THEIR ORBITS

INTERNATIONAL SPACE STATION: https://youtu.be/rfYJEI6KjFg
OFF THE EARTH, FOR THE EARTH,
AND BEYOND.

GEOSTATIONARY SATELLITE https://youtu.be/XzhVK09YReA

REINFORCEMENT TEST https://drive.google.com/file/d/1j
7H0zJVwY2vP6hJr6CpPpKyuD7979
zbY/view?usp=sharing

ANSWER (REINFORCEMENT TEST) https://drive.google.com/file/d/1s
SZoRbWc8PSaf98tIZbUzED3ua6vq
nd_/view?usp=sharing

17

ANSWER

EXERCISE 3.3

SECTION A Answer
B
No. C
1 B
2 B
3 D
4
5

SECTION B

6 a radius of the orbit of satellite
b Linear speed is inversely proportional to radius of the orbit.
When the radius of the orbit increases, the linear speed decreases

c radius of the earth, R = 6370 km
height of the satellite, h = 1000 km
Thus, r = R + h = 1000 + 6370 =7370 km
R = 7.370 x 106m

Thus, v = GM
R+h

( )v =
6.67 ×10−11 × 5.97 ×1024
7.370 ×106

v = 7.35×103 m s-1

d The satellite will fall to lower orbit and continue to orbit nearer to the earth
because the gravitational force becomes larger than the centripetal force. When
the satellite moves into the atmospheric layer, the friction between the air and
the satellite will produce a lot of heat that will cause the satellite to burn.

18

7 (a) (i)

(ii) Escape velocity at Mercury and Venus

(b) The value of acceleration due to gravity and escape velocity at Mercury is
smaller than at Venus

(c ) Mercury have smaller mass

19