prayer

Class rules
Be respectful: Treat teachers and classmates with courtesy and kindness.

Be on time: Arrive to class promptly and be prepared to learn.

Be attentive: Focus on the lesson and participate actively.

Raise your hand: Ask questions and participate in discussions politely.

Be honest: Do your own work and avoid cheating.

No bullying or harassment: Treat everyone with respect and dignity.

 GUESS THE
CORRECT WORD
ARE YOU READY?
O_T_R _P_C_
OUTER SPACE
S_T_L_I_E
SATELLITE
_R_I_S
ORBITS
C_R_U_A_ O_B_T
CIRCULAR ORBIT
G_A_I_Y
GRAVITY
 Orbital
Mechanics
ORBITAL MECHANICS IS THE STUDY OF
HOW ARTIFICIAL SATELLITES AND
SPACECRAFT MOVE
THROUGH SPACE. IT'S ESSENTIAL FOR
NAVIGATION, SATELLITE POSITIONING,
AND MISSION
PLANNING.
Satellite motion
Satellite motion is the
study of how satellites
orbit larger masses, such
as planets. Satellites can
be natural (moons and
planets) or artificial
objects sent into space
by humans.
 Artificial Satellite
- All started with the launch of
Sputink-1 on 4th October, 1957
- Nations around the world launched
fleet of artificial satellites to
support critical services:
▪ Telecommunication and broadcasting
▪ Banking and finance
▪ Weather forecast
▪ Climate monitoring
▪ Power grid
▪ Remote sensing
How many satellites are
there in space?

As of February 27, 2025,

there are approximately
7,086 Starlink satellites in
orbit, with 7,052 of them
actively working.
https://www.space.com/spacex-starlink-satellites.html
 Types of Orbits PAGE 3

Satellites can occupy a variety of

orbits around Earth, each with its
unique characteristics and advantages
for different purposes. Here are the
main types of satellite orbits:
 Low Earth Orbit (LEO) PAGE 3

Altitude: 160-2,000 km (100-1,200 miles)

Orbital period: 90-120 minutes
Advantages:
Short signal delay
High-resolution imaging
Faster data transmission
Easier access for launch and maintenance
Disadvantages:
Limited coverage area
Atmospheric drag requires frequent orbital adjustments
Increased risk of space debris collisions
 Medium Earth Orbit (MEO) PAGE 3

Altitude: 2,000-35,786 km (1,200-22,236 miles)

Orbital period: 2-12 hours
Advantages:
Wider coverage area than LEO
Less signal delay than GEO
Suitable for navigation satellites
Disadvantages:
More expensive to launch than LEO
Increased radiation exposure
 Geostationary Earth Orbit PAGE 3

(GEO)
Altitude: 35,786 km (22,236 miles)
Orbital period: 24 hours (same as Earth's rotation)
Advantages:
Appears stationary from Earth
Wide coverage area (can cover a large portion
of the globe)
Ideal for communication satellites and
broadcasting
Disadvantages:
Longer signal delay than LEO or MEO
More expensive to launch than LEO or MEO
Limited flexibility for coverage in polar regions
CIRCULAR ORBITS &

ORBITAL SPEED
 OBJECTIVES
Students will be able to

▸ know that for an object to move in a

01 circular orbit around a large object of mass
M at a radial distance r, it must have an
orbital speed v given by
A Circular orbit is defined as a special
case of an elliptical orbit where the
eccentricity is zero, resulting in a
constant radial distance from the
center. The orbital velocity in a
circular orbit decreases as the radius
increases.
 Remember that, for circular orbits, any orbiting body has a
velocity with a constant magnitude but an ever-changing
direction. The diagram below shows Jupiter’s moon Europa
orbiting Jupiter. The direction of the moon’s velocity always
points along a tangent to its orbital path, indicated by the blue
arrow. Jupiter’s gravity acts as a centripetal force, which we
know must always point radially inward, indicated by the red
arrow.
This relationship helps explain why the moon’s
orbital speed is constant: the gravitational
force has no component in the same direction
as the moon’s velocity. Thus, the magnitude of
the velocity does not change due to gravity, but
the direction constantly changes because the
gravitational force constantly redirects it along
a circular path. At any point in the orbit, the
directions of the two quantities always point at
a right angle, or 90∘,to each other.
 Before we practice some
calculations, it should be noted
that the universal gravitational
constant is found commonly
throughout astronomy and other
fields of physics and has an
unchanging value of
𝐺=6.67×10^-11m^3/kg.s^2.
 Example 1: Calculating Orbital Speed

For a satellite to follow a circular orbit

around Earth at a radius of 10 000 km, what
orbital speed must it have? Use a value of
5.97×10^24 kg for the mass of Earth and
6.67×10^11 m^3/kg⋅s^2 for the value of the
universal gravitational constant. Give your
answer to the nearest metre per second.
 Answer
Here, we are given values for 𝑀,𝑟,and 𝐺.Notice that 𝑟 is given in
kilometres,so we must convert to metres before we can use it
in the equation: 𝑟=10000=1.0×10^7m฀
We are now ready to substitute all of our values into the
orbital speed equation:
GRAVITATIONAL POTENTIAL ENERGY &
ESCAPE VELOCITY
GRAVITY PLAYS A KEY ROLE IN ASTRONOMY.
 GRAVITATIONAL
POTENTIAL ENERGY (GPE)

-ENERGY AN OBJECT HAS DUE TO ITS

POSITION IN A GRAVITATIONAL FIELD.
EXAMPLES OF APPLICATION
OF GPE
 FORMULA: U = - (G * M * M) / R

WHERE:
- U = GRAVITATIONAL POTENTIAL ENERGY(IN
JOULES)
- G = GRAVITATIONAL CONSTANT (6.674 × 10⁻¹¹
N·M²/KG²)
- M = MASS OF THE LARGER BODY(IN KG)
- M = MASS OF THE SMALLER BODY(IN KG)
- R = DISTANCE BETWEEN THE
CENTERS OF THE TWO MASSES(IN M)
KEY FEATURES OF GPE

- ALWAYS NEGATIVE (ENERGY REQUIRED

TO ESCAPE).
- THE CLOSER AN OBJECT IS TO A MASSIVE
BODY, THE MORE NEGATIVE ITS GPE.
- HIGHER ALTITUDE = HIGHER (LESS
NEGATIVE) GPE.
 SAMPLE PROBLEM

A 1000 KG SATELLITE IS
ORBITING EARTH AT AN
ALTITUDE OF 500 KM. GIVEN
THAT EARTH'S MASS IS 5.97 × 10²⁴
KG AND ITS RADIUS IS 6371 KM.
FIND ITS GPE .
 ESCAPE VELOCITY
MINIMUM SPEED NEEDED TO BREAK FREE
FROM A PLANET’S GRAVITATIONAL PULL.
WHY IS ESCAPE VELOCITY
IMPORTANT?
- DETERMINES IF ROCKETS OR CELESTIAL
BODIES CAN LEAVE A PLANET.
- ESSENTIAL FOR SPACE MISSIONS AND
PLANETARY EXPLORATION.
- HELPS UNDERSTAND BLACK HOLES AND
EVENT HORIZONS.
APPLICATIONS OF ESCAPE
VELOCITY
 FORMULA: V = SQRT(2GM/R)

WHERE:
- V = ESCAPE VELOCITY (IN KM\S)
- G = GRAVITATIONAL CONSTANT
(6.674 × 10⁻¹¹ N·M²/KG²)
- M = MASS OF THE CELESTIAL
BODY( IN KG )
- R = RADIUS OF THE CELESTIAL
BODY (IN M)
 SAMPLE PROBLEM

A 1000 KG SATELLITE IS
ORBITING EARTH AT AN
ALTITUDE OF 500 KM. GIVEN
THAT EARTH'S MASS IS 5.97 ×
10²⁴ KG AND ITS RADIUS IS
6371 KM.FIND THE ESCAPE
VELOCITY .
 CONCLUSION
- GPE EXPLAINS WHY OBJECTS
STAY BOUND TO PLANETS.
- ESCAPE VELOCITY EXPLAINS
HOW OBJECTS LEAVE PLANETS.
-BOTH ARE FUNDAMENTAL
CONCEPTS IN SPACE
EXPLORATION.
QUESTIONS?
Unveiling the Bizarre Beyond the Known Cosmic Curiosities

ELLIPTICAL ORBITS
AND
ORBITAL PERIODS
Astronomy
Unveiling the Bizarre Beyond the Known Cosmic Curiosities

WHAT IS AN ORBIT?

• An orbit is the path an object follows around

another due to gravity.

• Most orbits in space are elliptical (oval-

shaped), not perfect circles.

• Examples: Planets orbiting the Sun

Unveiling the Bizarre Beyond the Known Cosmic Curiosities

WHY ARE ORBITS ELLIPTICAL?

• The force of gravity and the motion of

a planet combine to create an
elliptical orbit.
• A perfect circle requires a very
specific balance of forces, which is
rare in space.
• Elliptical orbits allow planets to move
at different speeds depending on their
position.
Unveiling the Bizarre Beyond the Known Cosmic Curiosities

WHAT IS ORBITAL PERIOD?

• Orbital period is the time

taken by an object to complete
one full orbit.

• It depends on the object’s

distance from the central body
and the gravitational force
Unveiling the Bizarre Beyond the Known Cosmic Curiosities

EXAMPLES OF
ORBITAL PERIOD

• Earth: 365.25 days

• Mars: 687 days
• Jupiter: 12 years
• The Moon: 27.3 days around
Earth
 Unveiling the Bizarre Beyond the Known Cosmic Curiosities

FACTORS AFFECTING ORBITAL PERIOD

• Distance from the central body: The farther an object is, the longer its orbital
period.

• Mass of the central body: More massive objects create stronger gravity,
influencing the orbit.
Unveiling the Bizarre Beyond the Known Cosmic Curiosities

SUMMARY

• Orbits are mostly elliptical,

caused by gravity and motion.

• Orbital period is the time

taken to complete one full
orbit.

• Distance, gravity, and speed

Unveiling the Bizarre Beyond the Known Cosmic Curiosities

THANKYOU
For Listening!
 GROUP
GROUP
ACTIVITY
Part 1:Circular Orbit Simulation
Draw the Orbit:
Use a compass or trace a round object to draw a large circle on your paper or
poster board.
This circle represents the satellite's orbit around Earth.
Mark Earth’s Position:
Draw a smaller circle in the center of the large circle to represent Earth.
Label it as "Earth."
Place the Satellite:
Take a small object (a ball, paper cutout, or even a coin) and place it on the
orbit.
This represents the satellite moving around Earth in a circular path.
Part 2:Escape Velocity Experiment
1. Use a rubber band or ruler to launch a
marble from the surface of a drawn circle
(Earth).
2. Try launching at different speeds.
3. Record what happens.
Part 3: Elliptical Orbits
1. Use string and two pushpins to create an
elliptical orbit on paper.
2. Place Earth at one focus of the ellipse.
3. Trace the orbit and observe.