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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Welcome, future scientists and engineers! Today, we are exploring one of the most exciting topics in physics: Projectile Motion. Have you ever kicked a football and watched its beautiful curved path? Or thrown a stone into a river? Or seen water spraying from a hose? All these are examples of projectile motion. In Ghana, we see this everywhere – from the arc of a football during an Inter-Co match, to a fisherman casting his net at the Jamestown harbour, to the spray of water from an irrigation system on a farm in the Afram Plains. Understanding projectile motion allows us to predict where an object will go, how high it will travel, and how long it will stay in the air.
What is a Projectile?
A projectile is any object that is thrown, kicked, or otherwise launched into the air and then moves under the sole influence of gravity.
Crucial Assumption: For our calculations in SHS physics, we will ignore air resistance. This simplifies the problem and allows us to focus on the effect of gravity. The Two Independent Motions
The most important idea in understanding projectile motion is that the movement can be broken down into two separate and independent parts: Horizontal Motion (x-direction): There is no acceleration in the horizontal direction (since we ignore air resistance). This means the horizontal velocity (`vx`) is constant throughout the flight. The only equation we need for the horizontal part is: `Distance = Velocity × Time` or `sx = ux * t` Vertical Motion (y-direction): The object is constantly accelerated downwards by gravity. The acceleration is constant and is equal to `g` (acceleration due to gravity, approximately `9.8 m/s²` or sometimes `10 m/s²` for easier calculation). Since gravity acts downwards, we use `a = -g`. The standard equations of linear motion apply here: `vy = uy + at` -> `vy = uy - gt` `s = ut + ½at²` -> `sy = uyt - ½gt²` `v² = u² + 2as` -> `vy² = uy² - 2gsy` Resolving Initial Velocity