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: 5
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 physics behind satellites, which are essential to our modern lives in Ghana. From watching DSTV and using GPS on our phones to forecast the weather for our farmers, satellites play a crucial role. We will build upon our previous knowledge of circular motion and Newton's Law of Universal Gravitation to understand how these objects stay in orbit. We will learn to derive the mathematical relationship that governs their motion and see how Ghana itself is a participant in space technology with its own satellite, GhanaSat-1.
A. Foundational Concepts (Recap)
Before we look at satellites, let's remember two key principles we have already learned: Newton's Law of Universal Gravitation: Every particle attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres. Formula: F_g = G * (M * m) / r² Where: `F_g` is the gravitational force. `G` is the universal gravitational constant (≈ 6.67 x 10⁻¹¹ Nm²kg⁻²). `M` is the mass of the larger body (e.g., Earth). `m` is the mass of the smaller body (the satellite). `r` is the distance between the centres of the two bodies (orbital radius). Centripetal Force: An object moving in a circle experiences a force that is directed towards the centre of the circle. This force is what keeps the object from moving in a straight line. Formula: F_c = m * v² / r Where: `F_c` is the centripetal force. `m` is the mass of the object moving in a circle (the satellite). `v` is the orbital speed of the object. `r` is the radius of the circular path. B. The Physics of a Satellite in Orbit
For a satellite to stay in a stable circular orbit around the Earth (or any large celestial body), there must be a force pulling it towards the centre. This force is the gravitational force exerted by the Earth. This gravitational force *is* the centripetal force.
Therefore, we can set the two equations equal to each other: Gravitational Force = Centripetal Force F_g = F_c C. Deduction of the Period of a Satellite