Lesson Notes By Weeks and Term - Junior Secondary 2

TERM – 2^ND TERM

WEEK NINE

Class: Junior Secondary School 2

Age: 13 years

Duration: 40 minutes of 5 periods each

Date:

Subject: BASIC TECHNOLOGY

Topic:  FRICTION

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

1. Define friction
2. Identify the causes of friction
3. Identify the effects of friction
4. Identify the advantages and disadvantages of friction

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS:   Videos, loud speaker, textbook, pictures,

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

NOTE

 FRICTION

Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact. It acts parallel to the surfaces and is caused by the interactions between the molecules of the materials in contact.

 Causes of Friction

The causes of friction arise from interactions between the molecules of materials in contact. There are primarily two types of friction: static friction and kinetic friction. The main causes include:

1. Surface Roughness: Irregularities and roughness on the surfaces in contact create more contact points, leading to higher friction.
2. Intermolecular Forces: The forces between molecules at the microscopic level result in resistance to motion when surfaces are in contact.
3. Adhesion: Adhesion is the attraction between different molecules at the interface of two materials, causing them to stick together and resist relative motion.
4. Temperature: Friction can be influenced by temperature changes. For instance, increased temperature may reduce viscosity, affecting lubrication.
5. Material Properties: The type of materials in contact affects friction. Different materials have varying coefficients of friction, determining the amount of resistance.

Effects of Friction

Friction has various effects, both positive and negative, in different contexts. Below are some key effects of friction:

1. Positive Effects:

   - Traction: Friction provides the necessary grip between tires and the road, ensuring traction for vehicles to move safely.

   - Walking: Friction between shoes and the ground allows people to walk without slipping.

2. Negative Effects:

   - Wear and Tear: Friction between moving parts in machines can lead to wear and tear, reducing the lifespan of components.

   - Energy Loss: Friction converts kinetic energy into heat, resulting in energy loss and reduced efficiency in machines.

   - Heat Generation: Excessive friction can cause overheating, leading to damage or malfunction of machinery.

   - Noise Production: Friction between surfaces can produce undesirable noise, impacting the comfort and efficiency of mechanical systems.

   - Difficulty in Motion: Friction opposes the motion of objects, making it more challenging to move them or change their state of motion.

Advantages of Friction

1. Friction provides the necessary grip for vehicles to move safely on roads, preventing slipping and accidents.
2. Friction between shoes and the ground allows people to walk or run without sliding.
3. Friction is essential for braking systems in vehicles, helping to slow down and stop the motion of the vehicle.
4. Controlled friction is utilized in welding and metalworking processes, allowing materials to be joined together.
5. Friction between a pen or pencil and paper is necessary for writing and drawing.
6. In machines, friction facilitates the transmission of power by providing grip and preventing slipping.

Disadvantages of Friction

1. Friction converts kinetic energy into heat, leading to energy loss and reduced efficiency in machines.
2. Friction between moving parts in machines can cause wear and tear, reducing the lifespan of components.
3. Excessive friction can result in overheating, leading to damage or malfunction of machinery.
4. Friction opposes the motion of objects, making it more challenging to move them or change their state of motion.
5. Friction between surfaces can produce undesirable noise, impacting the comfort and efficiency of mechanical systems.
6. In vehicles, friction contributes to energy loss, requiring more fuel to overcome resistance and maintain motion.
7. High friction can limit the speed at which objects can move, especially in transportation systems.

EVALUATION: 1. What is friction?

2. Identify and describe 3 causes of friction.
3. Mention 5 advantages and 5 disadvantages of friction.
4. Identify 4 negative effects of friction.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively