Lesson Notes By Weeks and Term v4 - SHS 2
BASIC PHYSICS
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BASIC PHYSICS
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Subject: Physics
Class: SHS 2
Term: 1st Term
Week: 4
Grade code: 2.1.1.LI.2
Strand code: 1
Sub-strand code: 1
Content standard code: 2.1.1.CS.3
Indicator code: 2.1.1.LI.2
Theme: MECHANICS AND MATTER
Subtheme: BASIC PHYSICS
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This lesson introduces the fundamental concept of adding vectors to find a 'resultant' or 'net' vector. In our daily lives in Ghana, we often encounter situations where multiple forces or motions act on an object at the same time. For instance, when a canoe crosses the Volta River, its own motion combines with the river's current. When two people pull a stubborn goat, their combined effort determines where the goat moves. Understanding how to calculate the combined effect (the resultant) is a crucial skill in Physics, with applications in engineering, navigation, and even sports.
A. Recap: Scalars and Vectors Scalar Quantity: A quantity that has only magnitude (size or amount). Examples: distance (5 km), speed (80 km/h), mass (50 kg), time (15 s). Vector Quantity: A quantity that has both magnitude and direction. Examples: displacement (5 km, East), velocity (80 km/h, North), force (20 N, downwards), acceleration (9.8 m/s², downwards).
We represent vectors with arrows. The length of the arrow shows the magnitude, and the arrowhead shows the direction. B. What is a Resultant Vector? The resultant vector is the single vector that has the same effect as two or more vectors combined. It is the sum of the vectors. Analogy: Imagine you walk from the school gate 30 metres East to the classroom block, and then 40 metres North to the library. Your total displacement is the straight-line path from the gate directly to the library. That direct path is the resultant displacement. C. Method 1: The Graphical Method (Scale Drawing)
This method involves drawing the vectors to scale and in the correct direction on paper. We use two main laws which give the same result.
i. The Triangle Law of Vector Addition (Tip-to-Tail Method) If two vectors are represented by two sides of a triangle in sequence, then the third closing side of the triangle, drawn from the tail of the first vector to the tip of the second vector, represents the resultant vector in both magnitude and direction.