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.2
Strand code: 1
Sub-strand code: 1
Content standard code: 3.1.1.CS.2
Indicator code: 3.1.1.LI.2
Theme: MECHANICS AND MATTER
Subtheme: BASIC PHYSICS
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Welcome, future scientists and engineers! Today, we explore one of the most fundamental forces in the universe: gravity. We see its effects every day – a mango falling from a tree, the reason we stay on the ground in Accra, Kumasi, or anywhere on Earth. But what is the deep connection between this everyday falling (`g`) and the grand force that holds the Moon in orbit around the Earth and the Earth around the Sun (`G`)? This lesson will bridge that gap. We will deduce, or derive, the mathematical relationship that connects the local acceleration due to gravity (`g`) that we feel here in Ghana, to the universal constant of gravitation (`G`) that applies everywhere in the cosmos.
This lesson involves connecting two famous laws from Sir Isaac Newton. Let's review them first before we bring them together. Concept 1: Force of Gravity (Weight) and Newton's Second Law
You already know from earlier studies that the force of gravity acting on an object near the Earth's surface is called its weight (W). According to Newton's Second Law of Motion, Force equals mass times acceleration (`F = ma`).
When the force is weight (`W`) and the acceleration is the acceleration due to gravity (`g`), the formula becomes:
W = mg (Equation 1)