Gearing Basics and Devices Basic Science and Technology JSS 2 Third Term Scheme of work With Lesson Notes
THIRD TERM E-LEARNING NOTE
SUBJECT: BASIC TECHNOLOGY
CLASS: JSS 2
SCHEME OF WORK
WEEK TOPICS
- Revision of Last Term’s work
- Belt and Chain drives
- Belt and Chain drives (Contd.)
- Gears
- Gears (Contd.)
- Hydraulics and Pneumatic Machines
- Building Construction I: Site Preparation
- Building Construction II: Setting Out
- Building Services: Taps and Water supply
- Practical Projects
Basic Science and Technology JSS 2 Third Term Scheme of work With Lesson Notes
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BASIC TECHNOLOGY
1. In a pair of two meshed gears X and Y, gear Y with 45 teeth is driven by gear X having 60 teeth.
i. To calculate the gear ratio, we divide the number of teeth on gear Y by the number of teeth on gear X:
Gear Ratio = Number of teeth on gear Y / Number of teeth on gear X
Gear Ratio = 45 teeth / 60 teeth = 0.75
ii. To determine if it’s speed reduction or enlargement, we look at the gear ratio value.
– If the gear ratio is less than 1 (e.g., 0.75 in this case), it indicates a speed reduction. This means that gear Y will rotate slower than gear X but with more force.
– If the gear ratio is greater than 1, it indicates a speed enlargement. This means that gear Y will rotate faster than gear X but with less force.
2. A gear of 30 teeth meshed with another gear of 120 teeth is rotating at 4 rpm. We need to calculate the speed of the 30-tooth gear.
The gear ratio can be calculated by dividing the number of teeth on the driven gear (30 teeth) by the number of teeth on the driving gear (120 teeth):
Gear Ratio = Number of teeth on driven gear / Number of teeth on driving gear
Gear Ratio = 30 teeth / 120 teeth = 0.25
To calculate the speed of the 30-tooth gear, we multiply the gear ratio by the speed of the driving gear:
Speed of the 30-tooth gear = Gear Ratio * Speed of the driving gear
Speed of the 30-tooth gear = 0.25 * 4 rpm = 1 rpm
Therefore, the speed of the 30-tooth gear is 1 rpm.
3. Pneumatic devices and hydraulic devices are used in various applications. Here are five examples of each:
Pneumatic devices:
– Pneumatic cylinders: They convert compressed air into linear motion and are commonly used in automation systems.
– Pneumatic drills: These tools use compressed air to rotate a drill bit for drilling holes in materials.
– Pneumatic actuators: They convert compressed air into rotary motion and are used in control valves and robotic systems.
– Pneumatic brakes: Compressed air is used to apply force and control the braking system in vehicles and machinery.
– Pneumatic pumps: These devices use compressed air to transfer fluids or create pressure in various systems.
Hydraulic devices:
– Hydraulic jacks: They use hydraulic fluid to lift heavy objects by applying force.
– Hydraulic presses: These machines use hydraulic pressure to shape or compress materials.
– Hydraulic brakes: Hydraulic fluid is used to apply force and control the braking system in vehicles.
– Hydraulic motors: They convert hydraulic pressure into rotary motion to drive machinery and vehicles.
– Hydraulic excavators: These machines use hydraulic power to dig and move soil or other materials.
4. “The gearing system of a car” refers to the mechanism that transfers power from the car’s engine to its wheels through a series of gears. The gears in a car’s transmission system help in controlling the speed and torque applied to the wheels.
The gearing system of a car typically includes components such as:
– Gearbox: It contains multiple gears that can be engaged or disengaged to change the gear ratio and control the speed of the vehicle.
– Clutch: It allows for smooth engagement and disengagement of the gears by connecting or disconnecting the engine from the gearbox.
– Differential: It splits the power from the transmission to the wheels, allowing them to rotate at different speeds when the car is turning.
The gearing system works as follows:
– When the driver shifts gears, the clutch is engaged to connect the engine to the gearbox.
– Depending on the desired speed and driving conditions, the driver selects the appropriate gear.
– The selected gear engages with the corresponding gear in the gearbox, creating a specific gear ratio.
– As the engine rotates, power is transmitted through the gears, which control the speed and torque applied to the wheels.
– The gear ratio determines how many times the engine’s rotation is translated into the rotation of the wheels.
– Lower gears provide higher torque for starting and climbing hills, while higher gears allow for higher speeds at lower engine RPMs.
– The differential ensures that power is distributed evenly between the wheels, allowing them to rotate at different speeds during turns.
5.
Imagine five gears placed next to each other, with their teeth interlocking or meshing with each other. The gears can have different sizes and number of teeth. The teeth of adjacent gears engage with each other to transmit rotational motion.
Here’s a verbal description of the five meshed gears:
– Gear A: It has 20 teeth and is connected to gear B.
– Gear B: It has 30 teeth and is connected to gears A and C.
– Gear C: It has 25 teeth and is connected to gears B and D.
– Gear D: It has 35 teeth and is connected to gears C and E.
– Gear E: It has 40 teeth and is connected to gear D.
In this configuration, when one gear is rotated, the motion is transmitted to the adjacent gears, causing them to rotate as well. This allows for the transfer of power and the synchronization of motion between the gears.
Visualizing these gears can help you understand how the rotational motion is transmitted and how changes in gear sizes can affect speed and torque in a system.
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Evaluation
As a BASIC Science teacher, here are ten fill-in-the-blank questions related to the topic of BASIC TECHNOLOGY:
1. In a pair of two meshed gears X and Y, gear Y with 45 teeth is driven by gear X having 60 teeth.
i. Calculate the gear ratio: Gear Ratio = ________ / ________
a) 45 teeth / 60 teeth
b) 60 teeth / 45 teeth
c) 45 teeth + 60 teeth
ii. Determine if it’s speed reduction or enlargement. The gear ratio indicates a ________.
a) Speed reduction
b) Speed enlargement
c) No change in speed
2. A gear of 30 teeth meshed with another gear of 120 teeth rotating at 4 rpm. Calculate the speed of the 30-tooth gear: Speed of the 30-tooth gear = Gear Ratio * ________ rpm.
a) 4 rpm
b) 30 rpm
c) 120 rpm
3. State 5 pneumatic devices, and hydraulic devices.
Pneumatic devices:
a) __________
b) __________
c) __________
Hydraulic devices:
a) __________
b) __________
c) __________
4. Refer to the internet and explain “the gearing system of a car.”
The gearing system of a car refers to the mechanism that transfers power from the car’s ________ to its ________ through a series of gears.
5. Draw five meshed gears.
6. In a pair of two meshed gears, if the driving gear has 24 teeth and the driven gear has 48 teeth, the gear ratio is ________.
a) 0.5
b) 1
c) 2
7. A gear with 60 teeth meshes with another gear with 20 teeth. If the gear with 60 teeth rotates at 100 revolutions per minute (rpm), the speed of the gear with 20 teeth is ________ rpm.
a) 300
b) 100
c) 50
8. Pneumatic devices use ________ to operate.
a) Compressed air
b) Hydraulic fluid
c) Electricity
9. Hydraulic devices utilize ________ to generate power.
a) Compressed air
b) Hydraulic fluid
c) Electricity
10. The gearing system of a car helps in controlling the ________ and ________ applied to the wheels.
a) Speed, torque
b) Voltage, current
c) Frequency, wavelength
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Lesson Plan Presentation: BASIC TECHNOLOGY
Objective: By the end of this lesson, students will be able to understand and apply concepts related to meshed gears, gear ratios, speed reduction or enlargement, pneumatic and hydraulic devices, and the gearing system of a car.
Duration: 60 minutes
Materials:
– Chalkboard/whiteboard and markers
– Visual aids (diagrams, pictures)
– Internet access for researching the gearing system of a car
Introduction (5 minutes):
1. Greet the students and briefly introduce the topic of Basic Technology, focusing on gears and their applications.
2. Display images of various gears and ask the students if they have seen or used gears before.
3. Explain that gears play a crucial role in transmitting and controlling motion in machines and devices.
Main Body:
1. Meshed Gears and Gear Ratio (15 minutes):
a. Present the scenario of two meshed gears, X and Y, with gear Y having 45 teeth and gear X having 60 teeth.
b. Ask the students to calculate the gear ratio: Gear Ratio = Number of teeth on gear Y / Number of teeth on gear X.
c. Provide options and encourage students to choose the correct answer.
d. Discuss the correct answer and explain how gear ratio determines the relationship between the gears’ rotations.
2. Speed Reduction or Enlargement (10 minutes):
a. Ask the students to determine if the given gear ratio represents speed reduction or enlargement.
b. Provide options and give students time to select the correct answer.
c. Discuss the answer with the class, explaining the relationship between gear ratio and speed.
3. Calculation of Speed (10 minutes):
a. Present the scenario of a gear with 30 teeth meshed with another gear with 120 teeth, rotating at 4 rpm.
b. Ask the students to calculate the speed of the 30-tooth gear using the gear ratio.
c. Provide options for the students to choose the correct answer.
d. Discuss the answer and explain how gear ratios can be used to determine the speed of different gears in a system.
4. Pneumatic and Hydraulic Devices (10 minutes):
a. Introduce the concepts of pneumatic and hydraulic devices.
b. Discuss their applications and advantages.
c. Ask students to state five examples of pneumatic devices and five examples of hydraulic devices.
d. Engage the students by allowing them to participate and provide their answers.
e. List their responses on the board and discuss each device, emphasizing their uses and benefits.
5. The Gearing System of a Car (15 minutes):
a. Ask the students to search the internet and research the gearing system of a car.
b. Give them a specific timeframe to gather information.
c. Once the research time is over, ask students to share their findings and explain the gearing system of a car.
d. Summarize the information shared, emphasizing the role of gears in controlling speed and torque in a car.
Conclusion (5 minutes):
1. Recap the main points discussed during the lesson, including meshed gears, gear ratios, speed reduction or enlargement, pneumatic and hydraulic devices, and the gearing system of a car.
2. Ask if any students have questions or need further clarification.
3. Provide additional resources or references for further study on the topic.
4. Encourage students to explore practical applications of gears in their daily lives.
Assessment:
1. In-class participation and engagement during discussions and activities.
2. Correct answers to fill-in-the-blank questions or quizzes related to the lesson topics.
3. Ability to explain and apply the concepts learned in class.
Note: This lesson plan can be adapted and modified based on the specific classroom
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THIRD TERM EXAMINATION FOR JUNIOR SECONDARY SCHOOL JSS 2 BASIC SCIENCE
