Lesson Notes By Weeks and Term v4 - SHS 2
KINEMATICS
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KINEMATICS
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Subject: Physics
Class: SHS 2
Term: 1st Term
Week: 8
Grade code: 2.1.3.LI.2
Strand code: 1
Sub-strand code: 3
Content standard code: 2.1.3.CS.1
Indicator code: 2.1.3.LI.2
Theme: MECHANICS AND MATTER
Subtheme: KINEMATICS
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This lesson introduces the fascinating topic of projectile motion, which describes the path of any object thrown or launched into the air. We see this every day in Ghana: when a footballer from the Black Stars scores a goal, when a market woman tosses a mango into a basket, or even when water sprays from a hose. By understanding the physics behind this motion, we can predict exactly where an object will land and how high it will go. This knowledge is fundamental to fields like sports science, engineering, and even military science. In today's lesson, we will use the equations of motion we already know to analyse this two-dimensional movement.
2.1 What is a Projectile?
A projectile is any object that is thrown, kicked, or otherwise launched into the air and then moves under the influence of gravity alone. The path it follows is called its trajectory, which is typically a parabola.
Key Assumptions for our calculations: To make our analysis simpler, we will make two important assumptions: Air resistance is negligible. We pretend there is no friction from the air slowing the object down. The acceleration due to gravity, `g`, is constant (approximately 9.8 m/s² or 10 m/s² for calculations) and acts vertically downwards. 2.2 The Core Principle: Independence of Motion
This is the most important concept in projectile motion. The motion of a projectile is treated as two separate and independent motions happening at the same time: Horizontal Motion (x-direction): There is no acceleration in the horizontal direction (since we ignore air resistance). This means the horizontal velocity is constant throughout the flight. Vertical Motion (y-direction): The object experiences a constant downward acceleration equal to `g` (`-g` if we define "up" as positive). This motion is identical to an object thrown straight up into the air. 2.3 Resolving the Initial Velocity