Lesson Notes By Weeks and Term v4 - SHS 1
KINEMATICS
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KINEMATICS
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Subject: Physics
Class: SHS 1
Term: 1st Term
Week: 7
Grade code: 1.1.3.LI.2
Strand code: 1
Sub-strand code: 3
Content standard code: 1.1.3.CS.1
Indicator code: 1.1.3.LI.2
Theme: MECHANICS AND MATTER
Subtheme: KINEMATICS
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This lesson explores the language we use to describe motion: kinematics. Imagine a trotro driver at the 37 station. They start from rest, accelerate to pick up speed on the highway, and then decelerate to a stop at the next station. Or think about a footballer taking a penalty kick—the ball accelerates rapidly and then travels towards the goal. Kinematics gives us the tools (equations) to precisely describe and predict this kind of motion. Understanding these principles is fundamental to almost all other areas of physics and engineering.
Part 1: Foundational Terminologies (Recap)
Before we derive the equations, we must be very clear on the language we are using. Distance vs. Displacement: Distance is the total path length covered. It is a scalar quantity (it only has size, e.g., 100 metres). Displacement (s) is the change in position in a specific direction. It is a vector quantity (it has size and direction, e.g., 100 metres East). *Example:* If you walk 20 metres from the classroom door to the board and then walk 5 metres back, the distance you have travelled is 25 m. Your displacement, however, is only 15 m from the door. Speed vs. Velocity: Speed is the rate of change of distance. It is a scalar. `Average Speed = Total Distance / Total Time`. Velocity (u, v) is the rate of change of displacement. It is a vector. `Average Velocity = Total Displacement / Total Time`. We use u for initial velocity and v for final velocity. Acceleration (a): Acceleration is the rate of change of velocity. It is a vector. An object accelerates if its velocity changes—this can mean speeding up, slowing down, or changing direction. The formula for acceleration is: ``` a = (Final Velocity - Initial Velocity) / Time taken a = (v - u) / t ``` The S.I. unit for acceleration is metres per second squared (m/s² or ms⁻²). Positive acceleration means velocity is increasing. Negative acceleration (often called deceleration or retardation) means velocity is decreasing. Part 2: The Equations of Uniformly Accelerated Motion
These equations work only when acceleration is constant (uniform). This is a very important condition. We cannot use them if the acceleration is changing.
Let's consider an object that: Starts with an initial velocity, u. Moves with a constant acceleration, a. For a time interval, t. Reaches a final velocity, v. And covers a displacement, s.