Lesson Notes By Weeks and Term v3 - Primary 6
Simple Machines (i) Levers
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Simple Machines (i) Levers
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Subject: Basic Technology
Class: Primary 6
Term: 3rd Term
Week: 1
Theme: You And Energy
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collect and identify simple machines identify the parts of the lever list common uses of levers
is applied to the top.
Palm kernel cracker (manual type): Similar to a nutcracker, fulcrum is the hinge, load is the kernel, effort is applied to the handle.
3. Third Class Lever: Arrangement: The Effort is located between the Fulcrum and the Load.
Effect: Always multiplies distance or speed, but requires more force than the load (mechanical disadvantage).
Common Examples in Nigeria: Fishing rod: Fulcrum is the hand holding the rod near the reel, Effort is the other hand pulling the rod upwards, Load is the fish at the end of the line.
Broom/Mop: Fulcrum is one hand near the top, Effort is the other hand in the middle pushing/pulling, Load is the dust/dirt at the bottom. Tongs (for picking up food like puff-puff, akara, or hot coals): Fulcrum is the pivot point, Effort is applied by the hand in the middle, Load is the item being gripped at the end.
Human forearm (lifting a weight): Fulcrum is the elbow joint, Effort is applied by the biceps muscle, Load is the weight in the hand.
Shovel (when throwing soil): Fulcrum is one hand holding the top of the handle, Effort is the other hand in the middle providing lift, Load is the soil on the shovel blade. A. Introduction to Simple Machines A simple machine is a mechanical device that changes the direction or magnitude of a force. They do not reduce the amount of work done, but they make doing the work easier by either: Reducing the force required (mechanical advantage). Changing the direction of the force. Increasing the distance or speed of movement. Examples of simple machines include levers, pulleys, inclined planes, wedges, screws, and wheels and axles. This lesson focuses specifically on levers. B. Levers A lever is a simple machine consisting of a rigid bar or beam that pivots around a fixed point. It is used to multiply force, change the direction of force, or multiply distance.
C. Parts of a Lever Every lever has three main parts:
1. Fulcrum (or Pivot): This is the fixed point around which the lever rotates or pivots. It is the support point.
Example: In a see-saw, the central support is the fulcrum. In a wheelbarrow, the wheel axle acts as the fulcrum.
2. Load: This is the object or resistance that needs to be moved or lifted. It is the force being overcome.
Example: In a see-saw, the person or object being lifted is the load. In a wheelbarrow, the sand, cement, or farm produce carried inside is the load.
3. Effort: This is the force applied to the lever to move the load. It is the force exerted by the user.
Example: In a see-saw, the push or pull by the person trying to lift the other end is the effort. In a wheelbarrow, the force exerted by the user on the handles to lift and move it is the effort. D. Classes of Levers Levers are classified into three classes based on the relative positions of the Fulcrum, Load, and Effort.
1. First Class Lever: Arrangement: The Fulcrum is located between the Effort and the Load.
Effect: Can multiply force, change the direction of force, or multiply distance.
Common Examples in Nigeria: See-saw: Fulcrum in the middle, children (Load and Effort) at either end. Crowbar (used to lift heavy objects or pull out nails): Fulcrum is the point where the crowbar rests on the ground/surface, Load is the object being lifted/nail, Effort is applied by hand.
Scissors: Fulcrum is the pivot screw, Load is the material being cut, Effort is applied to the handles.
Pliers: Similar to scissors, fulcrum is the pivot, load is the object being gripped, effort is applied to the handles.
Claw hammer (pulling a nail): Fulcrum is the edge of the hammer head resting on the wood, Load is the nail, Effort is applied to the handle. Digging stick/Leverage stick for uprooting cassava/yam: The stone or mound of earth used as a pivot is the fulcrum, the plant is the load, the hand applies the effort.
2. Second Class Lever: Arrangement: The Load is located between the Fulcrum and the Effort.
Effect: Always multiplies force (provides mechanical advantage), but does not change the direction of the force.
Common Examples in Nigeria: Wheelbarrow: Fulcrum is the wheel (axle), Load is the contents in the pan, Effort is applied to the handles to lift.
Nutcracker: Fulcrum is the hinge, Load is the nut, Effort is applied to the handles.
Bottle opener: Fulcrum is the edge of the bottle cap, Load is the cap's resistance, Effort is applied to the handle.
Stapler (when stapling): Fulcrum is the hinge at the back, Load is the staple pressing through papers, Effort is applied to the top.
Palm kernel cracker (manual type): Similar to a nutcracker, fulcrum is the hinge, load is the kernel, effort is applied to the handle.
3. Third Class Lever: Arrangement: The Effort is located between the Fulcrum and the Load.
Effect: Always multiplies distance or speed, but requires more force than the load (mechanical disadvantage).
Common Examples in Nigeria: Fishing rod: Fulcrum is the hand holding the rod near the reel, Effort is the other hand pulling the rod upwards, Load is the Teacher Activities: Introduction (10 minutes): Begin by asking learners to identify tools they use at home or on the farm (e.g., cutlass, hoe, wheelbarrow, spoon, bottle opener, scissors). Guide a discussion on how these tools make work easier. Introduce the term "simple machine." Focus the discussion on tools that pivot or rotate around a point. Introduce the term "lever" as a specific type of simple machine. Concept Explanation and Demonstration (20 minutes): Use a ruler and a pencil as a fulcrum to demonstrate a basic lever. Show how varying the fulcrum's position affects the force needed to lift a small object (e.g., an eraser). Clearly define and label the Fulcrum, Load, and Effort using the ruler demonstration. Present physical examples or clear diagrams of various levers (e.g., a pair of scissors, a bottle opener, a wheelbarrow, a broom). For each example, ask learners to identify the Fulcrum, Load, and Effort.
Classification of Levers (25 minutes): Explain the three classes of levers based on the relative positions of F-L-E. Provide multiple examples for each class, drawing from Nigerian contexts (e.g., crowbar for construction, wheelbarrow for farm work, tongs for frying akara). Use gestures or simple drawings on the board to illustrate the F-L-E arrangement for each class.
First Class:* F-L-E (e.g., see-saw, scissors, crowbar)
Second Class:* F-L-E (e.g., wheelbarrow, nutcracker, bottle opener)
Third Class:* F-L-E (e.g., fishing rod, tongs, broom)
Guided Application (15 minutes): Divide the class into small groups. Provide each group with pictures or actual simple machines (if available and safe). Instruct groups to identify the machine, classify it as a lever, and then identify the Fulcrum, Load, and Effort. Circulate among groups, providing support and correcting misconceptions.
Student Activities: Participate in the introductory discussion, naming tools and their uses. Observe the teacher's demonstration with the ruler and pencil, identifying the Fulcrum, Load, and Effort. Examine physical examples or diagrams of levers provided by the teacher. In groups, identify the parts (Fulcrum, Load, Effort) of various levers and classify them into their respective classes. Discuss and share their findings with the class. List common uses of levers in their homes and communities.
Question 1: Name three simple machines you might find in a Nigerian kitchen or compound and identify if they are levers.
Solution: Spoon/Fork: Yes, can act as a lever (e.g., prying open a lid).
Bottle opener: Yes, it is a second-class lever.
Pliers/Tongs: Yes, these are third-class levers (tongs) or first-class levers (pliers).
Commentary: This question helps students identify simple machines in their immediate environment and begin classifying them as levers.
Question 2: Consider a common wheelbarrow used for carrying sand or cement on a construction site. a) Where is the Fulcrum? b) Where is the Load? c) Where is the Effort?
Solution: a)
Fulcrum: The wheel (specifically, the axle where the wheel touches the ground). b)
Load: The sand or cement inside the tray of the wheelbarrow. c)
Effort: The force applied by the worker's hands on the handles to lift and push the wheelbarrow.
Commentary: This question directly targets the identification of the three parts of a lever using a very common Nigerian example.
Question 3: State two common uses for a pair of scissors and two common uses for a crowbar.
Solution: Scissors: Cutting fabric for sewing clothes (e.g., ankara, lace). Cutting paper for crafts or office work.
Crowbar: Prying open wooden crates or boxes (e.g., containing goods from the market). Removing nails from planks during construction or demolition.
Commentary: This question reinforces the practical application and utility of specific levers in daily Nigerian life.
Farming and Agriculture: Levers are crucial in Nigerian agriculture. A farmer uses a crowbar to uproot stubborn tree stumps or a digging stick (acting as a lever) to loosen soil. Wheelbarrows (second-class levers) are indispensable for transporting harvested crops, manure, or equipment across the farm. Understanding levers helps farmers choose appropriate tools and use them effectively to conserve energy.
Construction and Building: In Nigerian construction sites, levers are constantly in use. Crowbars are used to dismantle structures or lift heavy objects. Wheelbarrows transport sand, gravel, and cement. Workers might use planks as levers to move heavy beams or blocks. This knowledge is fundamental for understanding basic construction mechanics and safety.
Household Chores and Market Activities: Levers simplify many household tasks. Bottle openers (second-class levers) are used to open soft drink bottles. Scissors (first-class levers) are used for cutting fabric or paper. Tongs (third-class levers) are common for handling hot food like akara or roasted plantain. Even simple weighing scales in markets often employ lever principles to balance and measure goods. This demonstrates how simple machines are integrated into everyday life and commerce.