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: 1
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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Newton’s Third Law of Motion explains why things move the way they do when they interact—why a canoe moves forward when you paddle, why a gun “kicks” backward, why you can walk without slipping, and why rockets can move even in space. In Ghana, learners see these effects daily: pushing a wheelbarrow at the market, jumping during sports, riding a bicycle, or even when a trotro brakes suddenly. Understanding this law helps learners explain motion, improve safety, and apply science to technology and everyday problem-solving.
2.1 Force (Quick Reminder) A force is a push or pull that can change an object’s motion (speed or direction) or shape. Unit of force: newton (N). 2.2 Newton’s Third Law of Motion (Statement) Newton’s Third Law: > *For every action force, there is an equal and opposite reaction force.*
Meaning: Forces always occur in pairs. The two forces are: Equal in magnitude (same size) Opposite in direction Act on different objects Occur at the same time 2.3 Action–Reaction Force Pairs (How to Identify) To find a Newton’s Third Law pair, ask: Who is pushing/pulling? (Object A) What is being pushed/pulled? (Object B) Force on B by A = action Force on A by B = reaction (equal and opposite)
Important note: Action and reaction forces do not act on the same object, so they do not cancel each other.
2.4 Why Action and Reaction Do Not Cancel (Key Understanding) Learners often ask: “If forces are equal and opposite, why does anything move?”