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: 7
Grade code: 2.1.2.LI.4
Strand code: 1
Sub-strand code: 3
Content standard code: 2.1.2.CS.1
Indicator code: 2.1.2.LI.4
Theme: MECHANICS AND MATTER
Subtheme: KINEMATICS
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Welcome, students! Today, we are moving from studying how objects *move* (Kinematics) to understanding how they *behave* when forces try to change their shape. Have you ever wondered why the steel rods used in building houses in Accra are so strong, or why a rubber band stretches easily but a piece of fishing line is much harder to stretch? The answer lies in a property of the material itself. Understanding this property is crucial for engineers who build our bridges, architects who design our buildings, and even for tailors choosing the right thread.
This topic helps us understand the "stiffness" of a material. We need to learn three key terms: Stress, Strain, and Young's Modulus. a. Tensile Stress (σ)
When you pull on a wire or a rod, you are applying a force that tries to stretch it. The material inside resists this pull. Stress is a measure of how much force is applied *per unit of area* within the material. Definition: Tensile stress is the force applied per unit of cross-sectional area of a material. Formula: ``` Stress (σ) = Force (F) / Cross-sectional Area (A) σ = F / A ``` Explanation: Force (F): The pulling force (tension) applied to the material. Its unit is Newtons (N). Often, this is the weight of an object hanging from the wire (F = mg). Area (A): The area of the face of the material that is perpendicular to the force. For a wire or rod, this is the area of its circular cross-section. Its unit is square metres (m²). S.I. Unit: The unit for stress is Newtons per square metre (N/m²), which is also called a Pascal (Pa).