Lesson Notes By Weeks and Term v4 - SHS 3
BASIC PHYSICS
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BASIC PHYSICS
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Subject: Physics
Class: SHS 3
Term: 1st Term
Week: 4
Grade code: 3.1.1.LI.3
Strand code: 1
Sub-strand code: 1
Content standard code: 3.1.1.CS.2
Indicator code: 3.1.1.LI.3
Theme: MECHANICS AND MATTER
Subtheme: BASIC PHYSICS
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This lesson explores the fascinating physics that keeps satellites in orbit around the Earth and other celestial bodies. From the natural satellite we see almost every night, the Moon, to the artificial satellites that power our modern lives, the principles are the same. In Ghana, we rely on satellites every day without even thinking about it – for our DStv/GOtv channels, for the GPS on our phones to order a Bolt or find our way, and for weather forecasts that help our farmers.
2.1 What is a Satellite?
A satellite is any object that moves in a curved path, or orbit, around a planet or star.
There are two main types of satellites: Natural Satellites: These are celestial bodies that naturally orbit a larger body. The most common example is the Moon orbiting the Earth. Other planets also have moons (e.g., Jupiter has dozens). Artificial Satellites: These are man-made objects intentionally placed into orbit. They serve various purposes. A notable Ghanaian example is GhanaSat-1, our nation's first satellite, launched in 2017 to help with coastal monitoring. Other examples include communication satellites (for TV and internet), navigation satellites (for GPS), and weather satellites. 2.2 The Physics of Orbital Motion: The Balancing Act
To understand how a satellite orbits, we must recall two key concepts you have already learned: Newton's Law of Universal Gravitation: Any two objects with mass attract each other with a force. For a satellite of mass `m` orbiting the Earth of mass `M` at a distance `r` from the Earth's centre, this gravitational force `(F_g)` is: `F_g = (G * M * m) / r²` Where `G` is the universal gravitational constant (`6.67 x 10⁻¹¹ Nm²/kg²`). Centripetal Force: An object moving in a circle at a constant speed `v` is always accelerating towards the centre of the circle. This acceleration is caused by a net force called the centripetal force `(F_c)`. The formula is: `F_c = (m * v²) / r`