Lesson Notes By Weeks and Term v3 - Junior Secondary 1
Forces
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Forces
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Subject: Basic Science
Class: Junior Secondary 1
Term: 3rd Term
Week: 2
Theme: You And Energy
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Explain the meaningof for ce; Identify contact and non-contact for ces; Differentiatebetween magneticand gravitationalforces; measure and calculategravitational for ce(GF) when mass and height are provided Describe how to setup a balanced for ce Explain the meaningof friction, its uses,advantages and disadvantages
A force is a push or a pull that can cause an object to change its state of motion (start moving, stop moving, speed up, slow down, or change direction) or change its shape. In simpler terms, if an object's motion or shape changes, a force is acting on it.
Examples: Pushing a wheelbarrow filled with farm produce (e.g., yam, maize). Pulling a bucket of water from a well. Kicking a football during a match. The wind pushing against a tree. Squeezing a plastic bottle.
Unit of Force: The standard unit of force is the Newton (N), named after Sir Isaac Newton. Contact forces are forces that require direct physical contact between two interacting objects for the force to be exerted.
Examples: Friction: The force that opposes motion between two surfaces in contact. (e.g., the force that stops a car when brakes are applied; the force that allows you to walk without slipping on the ground).
Tension: The pulling force transmitted axially by a string, rope, chain, or similar one-dimensional continuous object. (e.g., pulling a load with a rope; the force in a clothesline).
Normal Force: The supporting force exerted by a surface on an object resting on it, acting perpendicular to the surface. (e.g., the force exerted by a table supporting a book; the ground supporting a person).
Applied Force: A force that is applied to an object by a person or another object. (e.g., pushing a door open; hitting a nail with a hammer).
Air Resistance (Drag): A type of frictional force exerted by air on objects moving through it. (e.g., a falling feather slowing down; a vehicle experiencing resistance as it moves). Nigerian Context
Examples: A farmer pushing a plough through the soil (applied force, friction). Students playing tug-of-war (tension, applied force). A market vendor pushing a "mai-ruwa" cart (applied force, friction). A fisherman pulling his net (tension). Non-contact forces are forces that act on an object without coming into physical contact with it. These forces can act over a distance.
Examples: Gravitational Force: The attractive force that exists between any two objects that have mass. On Earth, it is the force that pulls objects towards the Earth's center. (e.g., a ball thrown upwards eventually falls back down; a mango falling from a tree).
Magnetic Force: The attractive or repulsive force that acts between magnets or between a magnet and magnetic materials (like iron, nickel, cobalt). (e.g., a magnet picking up paper clips; compass needles aligning with the Earth's magnetic field).
Electrostatic Force: The attractive or repulsive force that exists between electrically charged objects. (e.g., a rubbed balloon sticking to a wall; static shock after walking on a carpet). Nigerian Context
Examples: A football kicked high up inevitably falling back to the pitch due to gravity. Magnets used in radio speakers or children's toys (magnetic force). Thunder and lightning in the sky involve electrostatic forces. Forces can be broadly classified into two main categories: contact forces and non-contact forces.
Understanding forces has numerous practical applications relevant to Nigerian contexts: Transportation and Road Safety: Braking Systems: The concept of friction is fundamental to how vehicles (cars, motorcycles, bicycles, lorries) stop. Effective braking relies on sufficient friction between brake pads and wheels, and between tyres and the road surface. Students can understand why smooth tyres are dangerous, especially during the rainy season, and why anti-lock braking systems (ABS) are important for maintaining control.
Movement of Vehicles: Forces like engine thrust, air resistance, and friction are all at play when a "danfo" bus or "okada" is moving. Understanding these helps in designing more efficient vehicles and safer road networks.
Construction and Engineering: Stability of Structures: Architects and engineers consider gravitational forces (weight of materials, people, and environmental loads) and balanced forces to design stable buildings, bridges (like the Eko Bridge), and flyovers that can withstand various stresses. The normal force from the ground supports the entire structure.
Lifting and Moving Heavy Objects: Contact forces (applied force, tension) are crucial in operating cranes, pulleys, and levers used in construction sites to lift heavy blocks or steel beams.
Agriculture and Rural Life: Ploughing and Farming: Farmers apply contact forces to push ploughs through the soil, overcoming friction to prepare land for planting. Understanding forces helps in designing more efficient farming tools.
Carrying and Transporting Goods: From carrying baskets of farm produce on heads (balanced forces, normal force) to pushing carts (applied force, friction), forces are central to daily agricultural activities and market logistics. Gravitational force makes things heavy, impacting how much can be carried.