Lesson Notes By Weeks and Term v4 - SHS 3
BASIC PHYSICS
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BASIC PHYSICS
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Subject: Physics
Class: SHS 3
Term: 1st Term
Week: 3
Grade code: 3.1.1.LI.3
Strand code: 1
Sub-strand code: 1
Content standard code: 3.1.1.CS.1
Indicator code: 3.1.1.LI.3
Theme: MECHANICS AND MATTER
Subtheme: BASIC PHYSICS
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This lesson introduces the fundamental concept of equilibrium. In our daily lives in Ghana, we see equilibrium in action everywhere, though we may not use the scientific term. We see it when a market seller in Makola Market perfectly balances a scale to sell gari, when a carpenter ensures a roof truss is stable, or even when a "trotro" driver skillfully loads the roof rack so that goods do not fall off on the journey from Accra to Kumasi. Understanding the conditions for equilibrium is crucial not just for passing WASSCE Physics, but for understanding the stability of structures all around us, from simple furniture to mighty bridges like the Adomi Bridge.
A. What is Equilibrium? In Physics, an object is said to be in equilibrium when its state of motion does not change. This can mean two things: The object is completely at rest (stationary). This is called static equilibrium. Example: A textbook resting on a table. The object is moving at a constant velocity (constant speed in a straight line). This is called dynamic equilibrium. Example: A car moving at a steady 50 km/h on a straight, flat road.
For a body to be in *complete equilibrium*, it must not be accelerating linearly and it must not be accelerating angularly (i.e., its rotation must not be speeding up or slowing down). To achieve this state of total balance, two conditions MUST be met. B. The First Condition: Translational Equilibrium (The Force Condition) This condition deals with forces. Forces are pushes or pulls that can cause an object to accelerate (change its velocity). For an object not to accelerate, all the forces acting on it must cancel each other out.
> First Condition of Equilibrium: The vector sum of all external forces acting on a body must be zero.
Mathematically, we write this as: ΣF = 0 (where Σ is the Greek letter 'Sigma', meaning "sum of")