1. Starter………. Write a new lesson title: ‘Solar System and Satellites’.
Stick in all three sheets!
Order: 1- ‘Objects orbiting larger objects: Thought experiment’.
2- ‘Circular motion in orbits’.
3- ‘Orbital speed and radius’.

2. Learning objectives…..
By the end of this lesson you should be able to…..
Describe the different types of satellite.
Describe and explain how an object orbits a bigger object.
Define velocity and acceleration.
Describe the acceleration and velocity of an satellite.
Explain how orbital speed and radius are related.

3. Learning objectives…..
 Describe the different types of satellites.

4. SATELLITES
These are objects that ORBIT a second more MASSIVE object.

5. For example:
MOONS – these orbit planets.
They are a type of NATURAL SATELLITE (i.e. they are not man-made).

6. ARTIFICIAL SATELLITES – these are satellites that HUMANS have BUILT.
There are lots orbiting the Earth and some orbiting the Sun and other planets.

7. Satellites in lower orbits TRAVEL FASTER than those in HIGHER ORBITS.
Artificial satellites in orbit around the Earth have DIFFERENT ORBITS ( polar orbits and geostationary orbits).
Satellites in lower orbits TRAVEL FASTER than those in HIGHER ORBITS.
The HIGHER the orbit of a satellite, the LONGER its 'PERIOD' (time to make one orbit).
The higher the orbit of a satellite, the longer its 'period' (time to make one orbit).

8. Satellites in LOW POLAR ORBIT pass over the POLES.
LOW POLAR ORBITS…..
Satellites in LOW POLAR ORBIT pass over the POLES.
They orbit between 100 km and 200 km above the Earth’s surface, taking around 90 MINUTES to make each orbit.
Satellites in low polar orbit pass over the poles. They orbit between 100 km and 200 km above the Earth’s surface, taking around 90 minutes to make each orbit. The Earth spins beneath the satellite as it moves, so the satellite can scan the whole surface of the Earth. Low orbit polar satellites have uses such as:
monitoring the weather
observing the Earth’s surface
military uses including spying

9. Low orbit polar satellites have uses such as: - MONITORING the WEATHER
LOW POLAR ORBITS
The Earth SPINS beneath the SATELLITE as it moves, so the satellite can SCAN the WHOLE SURFACE of the Earth.
Low orbit polar satellites have uses such as:
- MONITORING the WEATHER
- OBSERVING the EARTH’S SURFACE
- military uses including SPYING
Satellites in low polar orbit pass over the poles. They orbit between 100 km and 200 km above the Earth’s surface, taking around 90 minutes to make each orbit. The Earth spins beneath the satellite as it moves, so the satellite can scan the whole surface of the Earth. Low orbit polar satellites have uses such as:
monitoring the weather
observing the Earth’s surface
military uses including spying

10. GEOSTATIONARY SATELLITES
Geostationary satellites orbits ABOVE the EQUATOR.
The height of their orbit - 36,000 KM - is just the right distance so that it takes them ONE DAY (24 HOURS) to make each ORBIT.
This means that they stay in a FIXED POSITION over the EARTH’S SURFACE
Geostationary satellites have a different trajectory to polar satellites – they are in orbit above the equator. The height of their orbit - 36,000 km - is just the right distance so that it takes them one day (24 hours) to make each orbit. This means that they stay in a fixed position over the Earth’s surface. Geostationary satellites have uses such as:
communications - including satellite TV
global positioning or GPS - which is used for sat navs (satellite navigation systems)
Geostationary satellites always appear in the same position when seen from the ground. This is why satellite television dishes can be bolted into one position and do not need to move.

11. Geostationary satellites have uses such as:
Communications - including SATELLITE TV
- GLOBAL POSITIONING or GPS - which is used for sat navs (satellite navigation systems)
- Geostationary satellites always appear in the same position when seen from the ground. This is why satellite television dishes can be bolted into one position and do not need to move.

12. What to do…… Orbit Key details. Uses Geostationary Polar
-Communications - including satellite TV.
-Monitoring weather
-Observing the earth’s surface
-Military uses including spying
-GPS - which is used for sat nav.
Uses
Key detail
-The Earth spins beneath the satellite as it moves, so the satellite can scan the whole surface of the earth.
-The height of their orbit - 36,000 km - is just the right distance so that it takes them one day (24 hours) to make each orbit.
Complete the table.
2) Draw a diagram of the Earth – 2 satellites (one on a geostationary, one on a polar orbit).

13. Orbit
Key details.
Uses
Geostationary
-The height of their orbit - 36,000 km - is just the right distance so that it takes them one day (24 hours) to make each orbit.
-GPS - which is used for sat nav.
Polar
The Earth spins beneath the satellite as it moves, so the satellite can scan the whole surface of the earth.
-Military uses including spying.
-Observing the earth’s surface
-Monitoring weather

14. Learning objectives…..
 Describe and explain how an object orbits a bigger object.

15. Orbits – basics…..
Planets move around the Sun in almost CIRCULAR ORBITS.
The same is true for MOONS and ARTIFICIAL satellites orbiting planets.
But how does an object orbit a bigger object?
(Basic idea).
Gravity provides the FORCE which keeps an object within this ORBIT.

16. The first thing to understand is ……
…..the ONLY FORCE governing the motion of a satellite is the FORCE of GRAVITY.

17. NEWTON was the first to theorize that a OBJECT launched with SUFFICIENT SPEED would actually ORBIT the earth.
Why did many people accept Newton’s idea?
A: Isaac Newton was a respected scientist who had made new discoveries before.

18. To understand how an OBJECT can ORBIT the earth, here is a THOUGHT EXPERIMENT originally written by ISAAC NEWTON………………

19. Consider a projectile launched HORIZONTALLY from the TOP of the VERY HIGH MOUNTAIN.
*at a location high above the influence of air drag.

20. A B
As the projectile moves HORIZONTALLY in a direction tangent to the earth, the FORCE of GRAVITY would pull it DOWNWARD.
As the projectile moves HORIZONTALLY the FORCE of GRAVITY would pull it DOWNWARD.

21. A B
If the LAUNCH SPEED was TOO SMALL, it would eventually FALL to earth (object A and B).
Paths A and B illustrate the path of a projectile with INSUFFICIENT LAUNCH SPEED for ORBITAL MOTION.

22. C
But if launched with SUFFICIENT SPEED, the projectile would FALL TOWARDS the earth at the SAME RATE that the earth CURVES.

23. C
This would cause the PROJECTILE to stay the SAME HEIGHT above the EARTH and to ORBIT in a CIRCULAR PATH (such as path C).

24. At every point along its trajectory, a satellite is FALLING TOWARD the EARTH.
Yet because the EARTH CURVES, it NEVER REACHES the EARTH.

25. And at even GREATER LAUNCH SPEEDS, a cannonball would once more orbit the earth, but now in an ELLIPTICAL PATH (as in path D).

26. What to do……
WORD BANK: elliptical, same rate, insufficient, gravity, fall, curves, falling, curves, force.
Complete ‘fill in the blank task’.
Copy the diagram above.
Label object A,B and C. Draw in object D.

27. Learning objectives…..
By the end of this lesson you should be able to…..
 Define velocity and acceleration.

28. You need to be able to explain how VELOCITY and ACCELERATION of a satellites changes.
Before that we need to understand:
What velocity is.
What acceleration is.

29. Speed and velocity ……. Speed is how FAST an object is going.
E.g. 20 m/s.
It has NO REGARD to DIRECTION.
VELOCITY is how FAST an object is going, and in which DIRECTION.
E.g. 20 m/s north.

30. The cars below are ALL TRAVELING at the SAME SPEED of 0.5 m/s.
Q: Do they have the same velocity?
A: No.
They are all moving in different directions, so all have a different velocity.

31. You can have objects travelling at a CONSTANT SPEED with a CHANGING VELOCITY.
This happens when the object is CHANGING DIRECTION whilst staying at the SAME SPEED.
E.g. a CAR going around a ROUNDABOUT at a CONSTANT SPEED has a CONSTANTLY CHANGING VELOCITY.

32. Acceleration…… Acceleration is HOW QUICKLY the VELOCITY is CHANGING.
The change in velocity can be CHANGE IN SPEED, or a CHANGE IN DIRECTION, or BOTH.

33. Acceleration……
E.g. a CAR going around a ROUNDABOUT at a CONSTANT SPEED has a CONSTANTLY CHANGING VELOCITY……….
………. the car is therefore CONSTANTLY ACCELERATING.

34. Satellites………
Statellites orbitning a bigger object constantly changing velocity………
…….. And therefore constantly accelretig.

35. Mini- quiz……….. A: 1) Fast, direction. 2) velocity, changing,
COPY: VELOCITY is how f……………………. an object is going, and in which d……………………………….. E.g. 20 m/s north.
2) COPY: Acceleration is how quickly the v………………………….. is c…………………………….
A change in velocity can be change in s……………………………., or a change in d………………………………………., or both.
3) Is a car driving at a constant speed in a circle accelerating? Why?
A: 1) Fast, direction.
2) velocity, changing,
speed, direction.
3) Yes, it is changing direction, therefore changing velocity.

36. Learning objectives…..
By the end of this lesson you should be able to…..
Describe the acceleration and velocity of an satellite.

37. Recap: Newton’s first law:
An object at REST stays at REST and…….
…….. an object in MOTION stays in MOTION with the same SPEED and in the same DIRECTION ……..
…………………. unless acted upon by an UNBALANCED FORCE.

38. Recap: Newton’s first law:
For an object to ACCELERATE, there must be an UNBALANCED FORCE acting on it.

39. Circular motion in orbits……
Demo: Spinning bung.
Centripetal Force
For circular motion, this force is DIRECTED towards the CENTRE of the CIRCLE.
In the solar system, the force that is acting towards the centre of the circle is the GRAVITATIONAL FORCE (gravity) between a planet and the Sun (or a planet and its satellites).

40. ………….and the FORWARD MOTION (INSTANTANEOUS VELOCITY) of the object.
Centripetal Force
Instantaneous velocity
What would happen to the object if gravity suddenly disappeared?
An orbit is a BALANCE between the FORCE providing the ACCELERATION ……….
………….and the FORWARD MOTION (INSTANTANEOUS VELOCITY) of the object.

41. The object keeps ACCELERATING towards what it’s orbiting.
However, the instantaneous VELOCITY (which is at right angles to acceleration and to the force of gravity) keeps the object TRAVELLING in a CIRCLE.

42. What to do……..
WORD BANK: angles, circle,, gravity, force, towards, right, centre, unbalanced, velocity.
1) Complete worksheet.
2) Complete questions.
Questions…….
Q1. State what force keeps objects in orbit around the Sun.
Q2. In what direction does the force that keeps the Earth orbiting the Sun act on the Earth? A:
Q1. Gravity.
Q2. The force acts towards the centre of the Sun/the centre of the orbit.

43. Learning objectives…..
By the end of this lesson you should be able to…..
Explain how orbital speed and radius are related.

44. Orbital speed and radius…….
Demo: Spinning bung.
The SIZE of an ORBIT depends on the OBJECT’S SPEED.
The CLOSER you get to a STAR or PLANET, the STRONGER the GRAVITATIONAL FORCE.
The STRONGER the FORCE, the FASTER the ORBITING OBJECT needs to TRAVEL to REMAIN in ORBIT.

45. Demo: Spinning bung.
For an object in a STABLE ORBIT, if the SPEED of the OBJECT CHANGES, the SIZE (RADIUS) of its orbit MUST do so TOO.
If the object moves FASTER, the RADIUS of its orbit must be SMALLER.
If it moves SLOWER, the RADIUS must be LARGER.

46. What to do…….. 1) Complete worksheet.
WORD BANK: closer, stronger speed, faster, orbit, size, larger, gravitational force, smaller, larger.
1) Complete worksheet.
2) Complete question in full sentences.
Q. If the Earth moved towards the Sun, what would happen to the speed of its orbit, provided it were to remain in a stable orbit? Why?

47. Q. If the Earth moved towards the Sun, what would happen to the speed of its orbit, provided it were to remain in a stable orbit?
Why? A:
The speed of the orbit would increase, as greater force is acting, so a greater speed is needed to keep the Earth in stable orbit.

48. Homework…..
Complete the ‘band assessment’.
DUE TOMORROW.