ROTARY MOTION
Subject :
Basic Technology
Term :
Second Term
Week:
Week 10
Class :
JSS 3 / Basic 9
Topic:
ROTARY MOTION
Previous lesson :
The pupils have previous knowledge of
LINEAR MOTION
in Basic Science in their previous lesson
Behavioral Objectives : At the end of the lesson , pupils should be able to
- Define Gears, gearing and related calculations
- Linear Motion
- Rotary Motion
- Transmission of Motion
Instructional Materials :
- Wall charts
- Pictures
- Related Online Video
- Flash Cards
Methods of Teaching :
- Class Discussion
- Group Discussion
- Asking Questions
- Explanation
- Role Modelling
- Role Delegation
Reference Materials :
- Scheme of Work
- Online Information
- Textbooks
- Workbooks
- 9 Year Basic Education Curriculum
- Workbook
CONTENT
Topic: MECHANICAL ENERGY TRANSMISSION SYSTEM (Rotary Motion)
Content:
- Types of Rotary Motion
- Principles of Application
Rotary Motion: This is motion of a body moving in a circular form. Examples of circular motion is the rotation of a fan, vehicle tyres, the handle of the clock, etc. e.g.
Types of Rotary Motion
- A worm drive is an example of rotational motion.
A worm drive
- Both the worm and the worm gear—is rotating on its own axis.
Another example:
- In below image consider the motion of sphere which is blue colour ,
www.physics.indiana.edu.
- It has both circular and rotational motion.Because it completes a circular path while rotating around it’s axis.
- In below image a person is performing Somersault
img.sparknotes.com.
- This is also an example for rotational motion, because he is rotating about his axis.
Principles of Application
Conversion of Rotary Motion to Linear Motion
There are many instances when it is required that one type of motion, e.g. rotary motion at one point be converted to linear motion at another point, and vice-versa. Household sewing machines, motor vehicle engine and transmission systems, motor-cycles, screen wipers in motor vehicles, printing machines, etc., have several mechanisms which convert one type of motion at one point to different or similar type of motion at another point.
The up and down (reciprocating) motion of the piston and its mechanical energy inside an engine cylinder must be converted into the rotary motion and mechanical energy of the rotating crankshaft of the engine. The slider-crank mechanism shown below is utilized to accomplish this task. It consists of the piston (referred to as con-rod), and the crankshaft (referred to as crank). The piston slides up and down or reciprocates inside the cylinder. The crankshaft performs pure rotary motion. The connecting rod connects the crank to the piston. Its complex motion is such that at the connecting point A to the crank, it performs pure rotary motion as the crank while at the connecting point B to the connecting rod, it performs pure linear motion.
In the rack and pinion system shown below, the rotary motion given to the steering wheel by the driver is transmitted to the rotary motion of the pinion. The rotary motion of the pinion is converted into the linear motion of the rack which turns the tyres. The (a) fig below shows the steering system while (b) fig shows the details of the steering box containing the rack and pinion mechanism.
When the screw jack image below is secure placed under a vehicle for jacking, the rotary motion of the nut of the jack is converted to the upward or downward linear motion of the screw to lift or bring down the vehicle. In this mechanism, the screw has a square thread which engages the interval thread of the nut to achieve the above motions.
The metalworker’s vice, the woodworker’s vice, the pipe vice, and the G-clamp, which are all, work on the same principle as the screw jack described above.
Screw jack
Presentation
The topic is presented step by step
Step 1:
The class teacher revises the previous topics
Step 2.
He introduces the new topic
Step 3:
The class teacher allows the pupils to give their own examples and he corrects them when the needs arise
Conclusion
The class teacher wraps up or conclude the lesson by giving out short note to summarize the topic that he or she has just taught.
The class teacher also goes round to make sure that the notes are well copied or well written by the pupils.
He or she does the necessary corrections when and where the needs arise.
EVALUATION
- Define rotary motion
- Briefly explain the types of Rotary Motion
- Define Gears, gearing and related calculations
- Linear Motion
- Rotary Motion
- Transmission of Motion
Assessment
- How do you reduce the friction effect of gears?
- List uses of gears
