Lesson Notes By Weeks and Term v4 - SHS 3
KINEMATICS
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KINEMATICS
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Subject: Physics
Class: SHS 3
Term: 1st Term
Week: 11
Grade code: 3.1.1.LI.4
Strand code: 1
Sub-strand code: 2
Content standard code: 3.1.1.CS.3
Indicator code: 3.1.1.LI.4
Theme: MECHANICS AND MATTER
Subtheme: KINEMATICS
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This lesson revisits and deepens our understanding of Kinematics, the branch of mechanics that describes the motion of objects without considering the forces that cause the motion. We see kinematics in action every day in Ghana: a tro-tro accelerating from a bus stop in Madina, an Okada rider navigating traffic in Kumasi, a mango falling from a tree in the village, or a footballer from the Black Stars striking a ball. By mastering the equations of motion, we can predict an object's future position and velocity, a skill crucial for fields like engineering, transportation safety, and even sports science.
The foundation of solving kinematics problems rests on understanding the key physical quantities and the equations that connect them. The equations we will use are valid only when acceleration is constant (uniform). A. Key Physical Quantities (The "SUVAT" Variables) It's helpful to remember these five variables using the acronym SUVAT.
| Symbol | Quantity | Definition | SI Unit | Nature | | :--- | :--- | :--- | :--- | :--- | | s | Displacement | The change in position of an object. It is the straight-line distance and direction from the starting point to the ending point. | metre (m) | Vector | | u | Initial Velocity | The velocity of the object at the beginning of the time interval (at t=0). | metres per second (m/s) | Vector | | v | Final Velocity | The velocity of the object at the end of the time interval. | metres per second (m/s) | Vector | | a | Acceleration | The rate of change of velocity. It tells us how quickly the velocity is changing. | metres per second squared (m/s²) | Vector | | t | Time | The duration of the motion. | second (s) | Scalar |
Important Note: Velocity and acceleration are vectors. This means their direction is crucial. In one-dimensional problems (like the ones we are solving today), we use positive (+) and negative (-) signs to indicate direction. For example, motion to the right can be positive, and motion to the left negative. B. The Four Equations of Uniformly Accelerated Motion
These equations are the tools we use to solve kinematics problems. `v = u + at` This equation relates final velocity to initial velocity, acceleration, and time. It is derived directly from the definition of acceleration (`a = (v-u)/t`). *Use it when you don't know or don't need displacement (s).* `s = ut + ½at²` This equation calculates displacement when you know the initial velocity, acceleration, and time. *Use it when you don't know or don't need final velocity (v).* `v² = u² + 2as` This equation links final velocity, initial velocity, acceleration, and displacement. It's very useful because it does not involve time. *Use it when you don't know or don't need time (t).* `s = ½(u + v)t` This equation gives displacement based on the average velocity `(u+v)/2` and time. *Use it when you don't know or don't need acceleration (a).* C. Problem-Solving Strategy