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Friction (6)
This document discusses friction, including its definition as a force that opposes the relative motion between two surfaces in contact. It describes different types of friction like sliding friction, static friction, fluid friction, and rolling friction. It also discusses factors that influence friction like surface texture, lubricants, and how friction can be both advantageous and disadvantageous. For example, friction allows us to walk and grip objects but also leads to wear and reduces machine efficiency by converting mechanical energy to heat.
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Friction (6)
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- 2. AKASH.R VIIIth B C.K.S English School HASSAN
- 3. Sub topics • What is Friction • Surface Texture • Types of Friction • Sliding Friction • Static Friction • Fluid Friction • Rolling Friction • Lubricants • Increasing Friction • Reducing Friction • Advantages of Friction • Disadvantages of Friction
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- 5. WHAT IS FRICTION? We have learnt that a force is required to stop the movement of the body in motion. Then why doesn’t a swing not continue to move forever once you have given it a push? Or why does a ball not roll endlessly once you have kicked it , even if no force is applied to stop it? This is because of friction. Friction is a force that opposes motion between two surfaces that are touching. Frictional force always opposes motion, trying to stop the movement of one surface over another.
- 6. The amount offriction between two surfaces depends on: 1. The type of surfaces in contact. 2. The amount of force pressing the surfaces together. 3
- 7. What Creates MoreFriction? Rough Surfaces Rough surfaces have more microscopic hills & valleys. The rougher the surface, the greater the friction will be. Greater Force The amount of force exerted increases the amount of friction Changing the amounts of the surfaces that touch does NOT change the amount of friction. 4
- 8. Friction is greaterwhen surfaces are pushed together with more force. 5
- 9. SURFACE TEXTURE Forfriction the object moving should touch the surface ,then only there comes a frictional force. So a surface plays a very important role in frictional force. Surfaces can be smooth or rough. The smoother the surface is ,the lesser is the frictional force. That is a why a ball travels a great distance over a tiled floor than a carpeted floor.
- 10. TYPES OF FRICTION There are 4 types of friction: sliding Friction static friction Fluid friction Rolling Friction
- 11. SLIDING FRICTION Theminimum force required to make a body just to slide over the surface is called sliding reflection. Once a body starts sliding the sliding friction is reduced. It is less than static friction. It is the rubbing of bodies in sliding contact. Let’s take an example when a person is skiing through on the mountains, then it is a sliding friction. .
- 13. Sliding friction, iscreated by flat objects moving against each other. Sliding friction resists the motion of an object as it moves along a surface. 14
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- 16. STATIC FRICTION Whena force is applied on an object to move it but it doesn’t moves, as the force applied is balanced by the force of static friction, then this is called static friction. It ends with the beginning of sliding of the object at rest. A simple example for static friction is a wooden block kept on a table. Unless sufficient force is exerted, the block will not slide down the table because static friction holds it place and resists sliding.
- 17. FLUID FRICTION Thefriction caused by an object moving through something that engulfs it in a fluid. It opposes motion between objects traveling through fluids like air and water. A simple example for fluid friction is Air resistance and a swimmer swimming through water exhibits fluid friction.
- 18. ROLLING FRICTION Itis the resistance that occurs when a round object such as a ball or tire rolls on a flat surface. It is mainly caused by the deformation of the object , the deformation of the surface or both. Rolling Friction is much less than the sliding friction. A simple example for rolling friction is a car with its wheels moving or the roller skates which we use for skating.
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- 20. When the GreatPyramids were being build in ancient Egypt, they used logs as rollers under the giant blocks of granite instead of trying to slide the rocks along the ground.
- 21. LUBRICANTS A lubricantis a substance introduced between two moving surfaces to reduce the friction between them, improving its efficiency and reducing the wear. Lubricants include motor oil, wax, grease etc. A simple example for the use of lubricants is that machine are oiled from time to time to reduce the friction. Wax Oil
- 22. INCREASING FRICTION • There are many situations when we cannot do without Friction. To overcome skidding along a slippery surface we adopt measures to increase friction. • Kutcha roads get muddy and slippery during rains. It is not possible to walk or drive on such roads. For this sand and gravel are spread over the mud to make the road rough. • Tyres of our vehicles and also soles of the shoes are grooved. This increases friction. This helps easy rolling of vehicles on the road and also provides better gripping with shoes on floor. • Mountaineers also wear spiked shoes to increase friction while walking on snow.
- 23. Reducing Friction • Friction is reduced when the area of contact between the two rubbing surfaces is reduced. This is done with the help of rollers. Wheels of the rollers not only reduce the area of contact between two surfaces but also move smoothly. • Making the surfaces smooth also reduces friction, like cemented roads are more smoother than rough roads so it reduces friction. • Lubrication also helps in reducing friction. • Shaping of the object is also a very important method to reduce friction. The vehicals are streamlined, that is a fish or bird like shape. These shapes are either pointed or narrow in front and curved on sides. And so their shape reduces friction.
- 24. WHY FRICTION ISNECESSARY? OR ITS ADVANTAGES Friction is very necessary in our daily life. Friction helps us in walking conveniently. It saves us from slipping on a smooth and slippery surface. It also helps us in writing on piece of paper. It is not possible to draw or write on oily or butter paper. The moving and stopping of vehicles on the road also depends on friction. It is also helpful in eating or drinking something as it helps us to hold the food or drink in our hand. It is also helps us in lighting a match-stick by rubbing it along the rough surface on the sides of match-box. Like these there are many examples of it which are very necessary in our daily life.
- 25. WHEN FRICTION ISHARMFUL? OR ITS DISADVANTAGES As you know that friction is very important but it is very harmful too. As it acts all the time so it reduces the speed of the body in motion. For this additional force has to be applied from time to time to maintain motion and speed. For this, more energy or fuel is consumed so it results in the waste of energy. An object in motion over a surface gets heated on running at a speed and for a long distance. For this we have to adopt the cooling systems. Sometimes even the fire accidents in cars and trains take place because of too much frictional force. So even if friction is very helpful for us, it is dangerous too that is why it is also called necessary evil.
- 26. A force mustbe applied to break these welds.
- 27. Sometimes lack offriction can be harmful!
- 28. In machines withmoving parts, friction increases wear, produces heat and reduces efficiency. A cracked and worn disc brake pad 21
- 29. While friction allowsus to convert one form of motion to another, it also converts some energy into heat, noise, and wear and tear on material. Losing energy to these effects often reduces the efficiency of a machine. In automobiles and airplanes, friction converts some of the energy in the fuel into heat, noise, and wear and tear on the engine’s parts. Excess frictional heat can damage an engine and braking system. 22
- 30. Averaged over urbanand highway conditions, the average mechanical efficiency is around 52% for typical automobiles. Much of the energy is lost in overcoming friction in operating the engine. The types of friction include energy necessary for pumping (moving the intake and exhaust valves), energy to overcome rubbing friction, and energy required to operate accessories such as the air conditioner. 23 http://www.parcon.uci.edu/paper/Conservation/energy.htm
- 31. More friction meansmore heat and less motion. 24
- 32. Kick Start Gearin a motorcycle engine
- 33. Friction Reduction Waysto reduce friction Lubricants- Substances applied to surfaces to reduce the friction between them Switching from sliding friction to rolling friction by the use of ball bearings Make surfaces that rub together smoother 25