Friction CLASS 8 NCERT powerpoint presentation
- 1. FRICTION Swati Mathur, Science teacher, MLZS Hayathnagar 1
- 2. HAVE YOU EVER THOUGHT ?? Why any ball moving on a surface stops after travelling certain distance without the act of external force? Why vehicles slow down when brakes are applied ? Swati Mathur, Science teacher, MLZS Hayathnagar 2
- 3. Why it is difficult to walk on smooth and wet floor ? Why we fall when we step on banana peel? Swati Mathur, Science teacher, MLZS Hayathnagar 3
- 4. It is an opposing force that opposes the motion of one body over the surface of another body. Swati Mathur, Science teacher, MLZS Hayathnagar 4
- 5. • Frictional force comes to notice only when two surfaces comes in contact with each other (contact force). • It is offered by solid, liquids and gases. • It is maximum in solids and minimum in gases. Swati Mathur, Science teacher, MLZS Hayathnagar 5
- 6. • The surfaces of solids that appear to be smoother are not actually smooth they posses some irregularities that is ridges and grooves. • When these type of surfaces come in contact with other surface their ridges and grooves get interlocked and opposing force comes into notice which opposes the motion. Force of friction always act in opposite direction to motion of applied force. CAUSES OF FRICTION Swati Mathur, Science teacher, MLZS Hayathnagar 6
- 7. FACTORS AFFECTING FRICTION 1. NATURE OF SURFACES : Swati Mathur, Science teacher, MLZS Hayathnagar 7
- 8. Swati Mathur, Science teacher, MLZS Hayathnagar 8
- 9. Weight is a force acting on a matter due to gravity. 10N= 1kg Swati Mathur, Science teacher, MLZS Hayathnagar 9
- 10. ACTIVITY cloth Swati Mathur, Science teacher, MLZS Hayathnagar 10
- 11. 2. WEIGHT (NORMAL FORCE): More is the weight of the body more is the friction. Swati Mathur, Science teacher, MLZS Hayathnagar 11
- 12. Swati Mathur, Science teacher, MLZS Hayathnagar 12
- 13. •Friction is the force that opposes motion between any surfaces that are in contact. •There are four types of friction: static, sliding, rolling, and fluid friction. •Static, sliding, and rolling friction occur between solid surfaces. •Fluid friction occurs in fluids, which are liquids or gases. Swati Mathur, Science teacher, MLZS Hayathnagar 13
- 14. • Sliding friction is slightly smaller than the static friction. • We find it somewhat easier to move the box already in motion to get it started. • Static friction > Sliding friction > Rolling friction Swati Mathur, Science teacher, MLZS Hayathnagar 14
- 15. INCREASING AND REDUCING FRICTION INCREASING : Swati Mathur, Science teacher, MLZS Hayathnagar 15
- 16. Reducing: In some situations friction is undesirable and we would want to minimize it. When oil or grease is applied between the moving parts of a machine, a thin layer is formed there and moving surfaces do not directly rub each other. Interlocking of irregularities is avoided to a great extent and movement becomes smooth. The substances which reduce friction are called lubricants. Swati Mathur, Science teacher, MLZS Hayathnagar 16
- 17. Wheels reduce friction • When one body rolls over the surface of another body, the resistance to its motion is called rolling friction. • Rolling reduces friction. • Rolling friction is smaller than sliding friction. • Sliding is reduced in most machines by using ball bearings. Swati Mathur, Science teacher, MLZS Hayathnagar 17
- 18. Swati Mathur, Science teacher, MLZS Hayathnagar 18
- 19. Friction: A Necessary Evil Swati Mathur, Science teacher, MLZS Hayathnagar 19
- 20. FLUID FRICTION Swati Mathur, Science teacher, MLZS Hayathnagar 20
- 21. What we have learnt : • Force is an opposing force that opposes the motion of one body over the surface of another body. • Frictional force comes to notice only when two surfaces comes in contact with each other (contact force). • It is offered by solid, liquids and gases. • The surfaces of solids that appear to be smoother are not actually smooth they posses some irregularities that is ridges and grooves. When these type of surfaces come in contact with other surface their ridges and grooves get interlocked and opposing force comes into notice which opposes the motion. • Factors affecting friction: ✓ nature of surfaces….rough and smooth surfaces ✓ weight (normal force)….more is the weight of the object, more is the friction • There are four types of friction: static, sliding, rolling, and fluid friction. • Static, sliding, and rolling friction occur between solid surfaces. • Fluid friction occurs in fluids, which are liquids or gases. • Sliding friction is slightly smaller than the static friction. • Rolling friction is smaller than sliding friction. • Friction can be increased by making a surface rough. • Friction is sometimes undesirable. • Sliding is reduced in most machines by using ball bearings. • Friction can be reduced by lubricants. • Fluid friction can be minimized by giving suitable shapes to bodies, moving in fluids. https://youtu.be/M8LlytVuABA Friction https://youtu.be/Fd9a24c1iy4 Friction (5min) https://youtu.be/B6mi1-YoRT4 Frictional force Swati Mathur, Science teacher, MLZS Hayathnagar 21