Lesson Notes By Weeks and Term - Junior Secondary School 2

TERM: 2nd TERM

SUBJECT: BASIC TECHNOLOGY                                

CLASS:  JSS 2

REFERENCE MATERIALS 

1. MELROSE, Basic Science and Technology, Book 2
2. NERDC, Basic Technology for JSS, Book 2

WEEK TEN

TOPIC: FRICTION

CONTENT

• Meaning of Friction
• Advantages and Disadvantages of Friction
• How to Reduce Friction

MEANING OF FRICTION

When a body slides over the surface of another body, there is opposing force acting opposite to the direction of motion. This opposing force is called FRICTION. Friction is therefore the force that opposes the relative motion between two surfaces that are in contact. Friction is required in most of the things we do. For instance, to be able to run, friction is required between the shoe and the ground. Also, a car must maintain friction between its tyres and the road to be able to move forward. It is also important to note the following:

1. The rougher the surfaces rubbing against each other, the more the friction
2. The smoother the surfaces rubbing against each other, the less the friction

ADVANTAGES OF FRICTION

1. With the help of friction it is possible to walk freely.
2. Without friction the brake of a motor car cannot work.
3. Buildup of friction between the bolts and nuts help them to stay tightened.
4. A ladder positioned against a vertical wall will not slide due to friction between the ladder and the wall

DISADVANTAGES OF FRICTION

1. It reduces the efficiency of machines
2. It causes wear and tear in machines
3. It reduces motion
4. It causes the heating of engines

EVALUATION

1. What is friction?
2. State two advantages and two disadvantages of friction.

APPLICATIONS OF FRICTION

1. Friction between the matchbox and the matchstick creates light
2. In sharpening a knife with a file, friction is also employed
3. In sharpening a pencil, friction is required between the sharpener blade and the pencil for sharpening to take place.
4. Materials used for making floors in homes and offices must be of high friction to provide a firm grip for the feet.

HOW TO REDUCE FRICTION

1. Lubricating: This involves the use of oily substance such as oil, grease and other material, that makes surfaces smooth and slippery, thereby reducing heat, wear, friction and vibration caused when two or more surfaces rub together.
2. Polishing: Friction between two surfaces in contact can be reduced by polishing them
3. Streamlining: It helps to reduce friction due to the shape of an object
4. Use of belt drives and pulley

EVALUATION

1. State four methods of reducing friction
2. List four applications of friction

READING ASSIGNMENT 

Read more about METALWORK MACHINES

REFERENCE MATERIALS; 

• MELROSE BASIC SCIENCEBASIC TECHNOLOGY BOOK 1, page 77-79
• NERDC, Introductory Technology for JSS, book 3, pages 146 – 148

WEEKEND ASSIGNMENT

1. Lubricant oil and grease in engines are used to reduce………… A. Tension B. Friction C. Gravity D. Magnetic
2. A force that can slow moving objects is called ………….. A. Gravity B. Magnetic force C. Contact force D. Friction
3. ………. helps to reduce friction due to the shape of an object A. Polishing B. Streamlining C. Lubricating D. driving
4. Materials used for making floors in homes and offices must be of A. Low friction B. equal friction C. unequal friction D. high friction
5. Which of the following is not a method of reducing friction A. Heating B. Lubricating C. Streamlining D. Polishing.

THEORY 

1. List four applications of friction
2. State two advantages and two disadvantages of friction