What did a rough surface offers? 1. No friction 2. Less friction 3. More friction 4. Less heat
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A rough surface offers more friction.
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The answer is : More friction.
Why?
Friction refers to the forces that resist the relative motion of two surfaces sliding against each other. There are three major causes of friction - molecular adhesion, ploughing effect, and surface roughness.
Molecular adhesion refers to the forces that attract molecules to each other. This is the most important cause of friction. Ploughing refer to the deformation of the surface of a softer material due to a harder material sinking in to it. Thus some force is needed for the changing deformation as the two surface i contact slide against each other. The surface roughens resists relative movement of surface due to higher points of one surface obstructing the movement of higher points in the other surface. To overcome this obstruction either the higher points must be broken down. This process is called abrasion. Effect of surface roughness is also overcome by the higher points of one surface moving up and down the higher points of other surface. Both these processes require application of some force, which contributes to the total frictional force.
Increased surface roughness means that the average height and size of these high points on the surface is increased. This requires higher abrasive force to break them or to move up and down over them. This is why rougher surfaces have higher friction.
Three most common method of reducing friction are:
Making surfaces smooth
Applying lubrication between surfaces
Introduce a rolling member between two surfaces eliminate direct contact between two surfaces. The most common form if this is seen in use of rolling bearings.
Three most common method of reducing friction are:
Increase roughness of surface. For example some small knobs to be adjusted by movement of fingers have knurled surfaces to prevent friction.
Use of softer material such as a piece of cloth or a rubber sheet to avoid slipping. Foe example when cap of a bottle is stuck, we may use wrap piece of rough cloth on the cap to increase its roughness. This method works by increasing the ploughing effect,
Increase the normal pressure pressing the two surfaces together.
Why?
Friction refers to the forces that resist the relative motion of two surfaces sliding against each other. There are three major causes of friction - molecular adhesion, ploughing effect, and surface roughness.
Molecular adhesion refers to the forces that attract molecules to each other. This is the most important cause of friction. Ploughing refer to the deformation of the surface of a softer material due to a harder material sinking in to it. Thus some force is needed for the changing deformation as the two surface i contact slide against each other. The surface roughens resists relative movement of surface due to higher points of one surface obstructing the movement of higher points in the other surface. To overcome this obstruction either the higher points must be broken down. This process is called abrasion. Effect of surface roughness is also overcome by the higher points of one surface moving up and down the higher points of other surface. Both these processes require application of some force, which contributes to the total frictional force.
Increased surface roughness means that the average height and size of these high points on the surface is increased. This requires higher abrasive force to break them or to move up and down over them. This is why rougher surfaces have higher friction.
Three most common method of reducing friction are:
Making surfaces smooth
Applying lubrication between surfaces
Introduce a rolling member between two surfaces eliminate direct contact between two surfaces. The most common form if this is seen in use of rolling bearings.
Three most common method of reducing friction are:
Increase roughness of surface. For example some small knobs to be adjusted by movement of fingers have knurled surfaces to prevent friction.
Use of softer material such as a piece of cloth or a rubber sheet to avoid slipping. Foe example when cap of a bottle is stuck, we may use wrap piece of rough cloth on the cap to increase its roughness. This method works by increasing the ploughing effect,
Increase the normal pressure pressing the two surfaces together.
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