Lesson Notes By Weeks and Term v4 - JHS 3
FORCE AND MOTION
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FORCE AND MOTION
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Subject: Science
Class: JHS 3
Term: 3rd Term
Week: 2
Grade code: B9.4.4.2.1
Strand code: 4
Sub-strand code: 4
Content standard code: B9.4.4.2
Indicator code: B9.4.4.2.1
Theme: FORCES AND ENERGY
Subtheme: FORCE AND MOTION
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Force and motion explain why trotro moves, why a football speeds up when kicked, why passengers jerk forward when a driver brakes suddenly, and why it is easier to push an empty wheelbarrow than a loaded one. In Ghana, these ideas help learners understand road safety (seat belts, braking distance), sports (kicking, throwing), and simple machines used in farms and workshops.
A. Important Definitions Force (F): A push or pull that can change an object’s motion (speed or direction) or shape. Unit: newton (N) 1 N is the force that gives a 1 kg mass an acceleration of 1 m/s². Mass (m): Amount of matter in an object; also a measure of inertia. Unit: kilogram (kg) Acceleration (a): Rate of change of velocity with time. Unit: m/s² If velocity increases, acceleration is positive; if it decreases (slowing down), acceleration is negative (deceleration). Inertia: Tendency of an object to resist changes in its state of motion. More mass → more inertia. Momentum (p): Quantity of motion of a moving object. Formula: p = mv Unit: kg·m/s Momentum increases when mass or velocity increases.
B. Newton’s First Law of Motion (Law of Inertia) Statement: An object remains at rest or continues moving with constant velocity in a straight line unless acted upon by a net (unbalanced) external force.
Meaning (step-by-step): If the total force on an object is zero, it will not change its motion. “Constant velocity” means same speed and same direction. A change in speed or direction means there is a net force.
Everyday Ghana examples: When a trotro suddenly stops, passengers tend to move forward. Their bodies were moving and want to continue moving (inertia). A book on a table stays at rest because forces are balanced: weight downward and table’s reaction upward.