PHYSICS STUDYING NOTES FORM THREE
TOPIC 2: FRICTION
Friction;- Is the force which opposes(resist) motion of the body. If a block of wood is placed on a table it remains at rest unless it is acted upon by external force.
The applied force must exceed the maximum friction force between the block of wood and the table if the block is to be moved along the table.
Friction force between two surface in contact exist only when there is relative motion between the two contacting surface. The friction between two surfaces exists because of the nature of the bodies in contact.
Advantages of Friction
1. It helps in walking process(because friction force stop us from slipping over)
2. It helps cars to move onroads easily due to friction between car tyres and road
3. It helps in car braking system. Brakes rely on friction between the brake drum or pads and the wheels. In a bicycle, there are brake pads which clamp onto the wheel to slow it down.
Disadvantages of friction
1. Cause machinery to heat up and can cause wear and tear.
2. Cause machinery to be less efficient.
3. Cause machinery to produce noise.
Methods of Reducing Friction.
1. Polishing: polishing the surface , reduces the irregulaties and hence , reduces friction.
2. Lubrication; it provides a layer of the lubricant on which the bodies can easily slide.
3. Use of ball-bearing or roller bearing; Roller bearing help to convert sliding friction into a milder form rolling friction. Rolling friction is lesser than sliding friction.
4. Streamlining; fast cars,boats,planes etc.. have a streamlined body. This is to allow to easily flow by without offering much resistance. Flying birds have srreamlined bodies.
5. Use of correct combination of surfaces in contact: use of alloys on moving and sliding parts reduces friction because alloys have a low coefficient of friction.
Types Of Friction.
1. Static friction; an opposing force between two solid objects at rest. In simple words, when there is no relative motion between two solid objects in contact with each other, we describe the frictional force between them as static.
2. Dynamic friction: numerically equal to the force of opposition when a body is moving over the rough surface.
Laws of friction.
1. When an object is moving the friction is proportional and perpendicular to the normal force(N)
2. Friction is independent of the area of contact.
3. The coefficient of static friction is slightlty greater than the coefficient of kinetic friction.
4. Friction depends upon the nature of the surfaces in contact.
Form three Topics
>Scalar and Vector quantities and its differences
>Vector representation and methods of vector addition.
>Examples of vector addition
>The concept of frictio
>Advantages and disadvantages of friction
>Methods of reducing friction
>Types of friction and etc.
>Concave and convex mirrors
>Terms used in studying curved mirrors
>Laws of refraction and etc.
>Simple microscope
>Compound microscope
>Telescope
>Lens camera
>Human eyes and etc.
>The concept of heat
>Sources of thermal energy
>Difference between heat and temperature
>Thermal expansion of solid
>Demostration of expansion of solids.
>Concept of conduction of heat
>Good and bad conductors
>Concept of convection of heat
>Concept of radiation
>Heat capacity
>Specific heat capacity
>The behaviour of particles of matter by applying kinetic theory.
>Effect of impurities on boiling point.
>Concept of vapour
>Concept of humidity
>Formation of dew
>Concept of relative humidity
>Concept of electric current
>Electromotive force and potential difference
>Factors which determine the resistance of a conductor.
The above Topics Should be covered by Form three students before his starting of Form four class and more practices should be very important to help students to understand the topics and its applications in daily life.
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