A pulley is a wheel that has a smooth groove in its rim, with a rope passing through the groove. At times, there are loads that are too heavy to lift.
MEANING OF PULLEY
A pulley is a simple machine that is used to lift heavy objects. A simple machine for overcoming this difficulty is the pulley.
EXAMPLES OF PULLEY MACHINES
- Flag pole
- A sewing machine
- Photocopy machine
- Spring balance
- A grinder machine
- A modern elevator
- A crane
TYPES OF PULLEYS
Basically, there are two (2) types of pulleys:
Single Fixed Pulley
A fixed pulley’s wheel and axle stay in one place.
A good example of a fixed pulley is a flag pole: When you pull down on the rope, the direction of force is redirected by the pulley, and you raise the flag pole.
A movable pulley is a pulley that is free to move up and down, and is attached to a ceiling or other object by two lengths of the same rope.
Examples of movable pulleys include construction cranes, modern elevators, and some types of weight lifting machines at the gym.
A compound pulley is a combination of fixed and movable pulleys. The third type of pulley is the compound pulley, which consists of combinations of fixed and movable pulleys.
The more complex the pulley, the more the effort needed to move the object decreases.
Strategies & Activities
Step: Teacher revises the previous topic
Step 2: Teacher introduces the new topic.
Step3: Teacher endeavors to explain all the points to the pupils thoroughly.
Step 4: Teacher welcomes pupils’ questions.
Step 5: Teacher evaluates the pupils.
Assessment & Evaluation
- Give three examples of simple pulleys;
- State two applications of pulley machines;
- Differentiate between fixed and movable pulleys;
- Construct and use pulleys.
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