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: 10
Grade code: 3.1.1.LI.4
Strand code: 1
Sub-strand code: 1
Content standard code: 3.1.1.CS.3
Indicator code: 3.1.1.LI.4
Theme: MECHANICS AND MATTER
Subtheme: BASIC PHYSICS
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Welcome, future scientists and engineers! Today, we journey beyond our planet, beyond our Sun, and even beyond our own star system. We will explore the grand structures of the universe: galaxies, which are like massive cities of stars, and nebulae, the beautiful cosmic clouds where stars are born and die. Understanding these structures helps us appreciate our place in the universe. In Ghana, for centuries, our ancestors have looked up at the same stars, using them for navigation, farming, and storytelling. This lesson connects that ancient wisdom with modern physics.
2.1 What is a Galaxy?
A galaxy is a vast, gravitationally bound system consisting of stars, stellar remnants (like white dwarfs and neutron stars), interstellar gas, dust, and an important but invisible component called dark matter. Analogy: Think of a galaxy as a giant city. The stars are the buildings, the gas and dust are the roads and parks, and all of it is held together by the city's laws and infrastructure (gravity). Our own galaxy is called the Milky Way. When you see a faint, cloudy band of light across the night sky in a very dark place (like in the village, away from city lights), you are looking into the dense part of our own spiral galaxy. 2.2 Types of Galaxies
Galaxies are classified based on their shape or visual morphology. The main types are:
a) Spiral Galaxies Description: These galaxies have a flat, rotating disk of stars and gas, with a central bulge and "spiral arms" winding out from the centre. Components: Central Bulge: A dense collection of older, reddish stars. Disk & Arms: Contains younger, hotter, blue stars, along with significant amounts of gas and dust. This is where most new stars are formed. Halo: A spherical region surrounding the disk, containing old stars and globular clusters. Example: Our own Milky Way and the nearby Andromeda Galaxy.