Lesson Notes By Weeks and Term v4 - JHS 1
FORCE AND MOTION
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FORCE AND MOTION
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Subject: Science
Class: JHS 1
Term: 3rd Term
Week: 3
Grade code: B7.4.4.1.2
Strand code: 4
Sub-strand code: 4
Content standard code: B7.4.4.1
Indicator code: B7.4.4.1.2
Theme: FORCES AND ENERGY
Subtheme: FORCE AND MOTION
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In our daily life in Ghana, we see objects moving and stopping all the time: a trotro moving on the road, a football rolling on a dusty field, a wheelbarrow being pushed at the market, or a book resting on a table. Understanding Newton’s First Law of Motion helps learners explain why objects keep moving, why they stop, and what role forces like friction and pushes/pulls play. This knowledge supports safe road use, sports performance, and basic engineering thinking.
A. Force and Motion (Quick Recall) Force: a push or pull that can change an object’s motion (start, stop, speed up, slow down, or change direction). Motion: change in position of an object with time. Rest: an object is not changing its position relative to a reference point. B. Newton’s First Law of Motion (Law of Inertia) Statement (standard form): > *An object remains at rest, or continues to move with constant velocity in a straight line, unless acted upon by a net (unbalanced) external force.*
Meaning (break it down step-by-step): If an object is at rest, it will stay at rest unless a force makes it move. Example: A stone on the ground will not start moving unless someone kicks it or water pushes it. If an object is moving, it will keep moving at the same speed and in the same straight direction unless a force changes its motion. Example: A bicycle will keep moving forward, but it slows down because friction and air resistance act on it. C. Key Terms Needed to Explain the Law 1) Inertia Inertia is the tendency of an object to resist changes in its state of motion (resist starting to move, stopping, speeding up, slowing down, or changing direction). Mass and inertia: The more mass an object has, the greater its inertia. A loaded wheelbarrow is harder to start moving and harder to stop than an empty one.
Ghanaian example: Pushing an empty market trolley is easier than pushing a trolley full of yam. The full trolley has more mass → more inertia → resists change more. 2) Balanced and Unbalanced Forces (Net Force) Balanced forces: forces are equal in size and opposite in direction → net force = 0 N. Result: no change in motion. The object stays at rest or continues moving at constant speed in a straight line. Unbalanced forces: forces do not cancel → net force ≠ 0 N. Result: motion changes (accelerates, decelerates, or changes direction).
Important link to Newton’s First Law: Newton’s First Law describes what happens when net force is zero. 3) Constant Velocity Velocity includes speed and direction. “Constant velocity” means: same speed and same direction (straight line).