Lesson Notes By Weeks and Term v4 - SHS 3
DYNAMICS
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DYNAMICS
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Subject: Physics
Class: SHS 3
Term: 1st Term
Week: 14
Grade code: 3.1.3.LI.1
Strand code: 1
Sub-strand code: 3
Content standard code: 3.1.2.CS.1
Indicator code: 3.1.3.LI.1
Theme: MECHANICS AND MATTER
Subtheme: DYNAMICS
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This lesson introduces the concept of collisions, a fundamental interaction in physics that we observe every day. From a tro-tro moving in traffic, to footballers tackling each other on the pitch, to the simple act of playing marbles ('chaskele'), collisions are all around us. By understanding the principles that govern them, we can better understand road safety, design better sports equipment, and appreciate the laws of motion in our world. We will explore the two main categories of collisions—elastic and inelastic—by focusing on what happens to momentum and kinetic energy during the interaction.
This topic builds on your prior knowledge of momentum (p = mv) and kinetic energy (KE = ½mv²). A. The Foundation: Principle of Conservation of Linear Momentum Before we can classify collisions, we must understand one rule that applies to ALL of them in an isolated system (a system where no external forces like friction act). Principle: In any collision between two or more objects in an isolated system, the total momentum before the collision is equal to the total momentum after the collision. Formula: For two bodies, `m₁` and `m₂`, with initial velocities `u₁` and `u₂` and final velocities `v₁` and `v₂`:
`Total momentum before = Total momentum after` `m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂`
*Remember: Velocity (and therefore momentum) is a vector. In one-dimensional problems, we use positive (+) and negative (-) signs to show direction.* B. What is a Collision? A collision is a brief event in which two or more bodies exert strong forces on each other. This interaction causes a change in their motion (i.e., a change in their velocities and momentum).
The key to distinguishing types of collisions is to look at the total kinetic energy of the system. C. Type 1: Elastic Collisions This is the "perfect" or ideal type of collision. Definition: An elastic collision is one in which both linear momentum AND total kinetic energy are conserved. Conditions: Total momentum before = Total momentum after (`m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂`) Total kinetic energy before = Total kinetic energy after (`½m₁u₁² + ½m₂u₂² = ½m₁v₁² + ½m₂v₂²`) Characteristics: The objects bounce off each other perfectly after colliding. No energy is lost to sound, heat, or permanent change in shape (deformation). Examples in real life are rare approximations. The collision between billiard balls or air hockey pucks are very close to being elastic.