Friction is the force that opposes the relative motion between two surfaces of objects in contact. The force of friction always acts in a direction opposite to that of the applied force. Nature of surfaces in contact and mass of the body are the two main factors on which friction depends.
Friction always acts in a direction opposite to that of the applied force.
Friction comes into play when the surfaces of the two objects in contact get interlocked with each other. While sliding one surface over another, the time for interlocking is very small and hence interlocking is not as rigid as it would be if the two surfaces were stationary. Therefore, less force is required to overcome the interlocking when the surfaces are moving, and sliding friction is less than static friction.
The resistance to an object's motion through a particular fluid may be termed as fluid friction. For example, vehicles moving at high speed are opposed by air molecules.
Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface.
No, friction depends on the roughness/ smoothness of the surface.
In the static position, the irregularities of the two surfaces in contact are interlocked rigidly due to which more force is required to overcome the interlock. When an object is already sliding, the interlocking is not as deep, so a relatively smaller force is required to overcome the kinetic friction.
We know that friction occurs due to the irregularities of the surfaces in contact. A rough surface has more irregularities than a smooth surface, so the sliding friction will be greater in the rough surface.
Friction between surfaces can be reduced by the following methods:
• Applying lubricants to minimize the interlocking of irregularities
• Using a soap solution to make the surface slippery
• Spreading fine powder for parts that cannot have oil applied
• Polishing surfaces to reduce surface irregularities
• Streamlining shapes
• Converting sliding to rolling friction
When someone writes with chalk on the blackboard, the friction between the chalk piece and the blackboard causes some chalk particles to get separated from the piece of chalk, which stick to the blackboard.
Streamlining is a design or a form that minimises fluid friction. It provides very little resistance to the flow of air or water, thereby increasing speed and ease of movement. Birds and fish have naturally streamlined bodies, which make it easier for them to fly, swim or move with greater speeds.
The objects moving in the fluids have a streamlined shape because this shape helps in reducing the friction between the objects and the fluids which they are moving through.
Kabaddi players rub their hands with soil to get a better grip of their opponents. The mud increases the friction on their hands and provides a better grip..
It would be easier to drag the box which is covered with polythene because polythene has a smooth surface and experiences less friction as compared to jute. Hence, it requires less force to drag it.
A banana peel has a smooth surface which reduces the friction between the ground and our feet, making us slip.
Following are the advantages of friction:
• Helps in walking comfortably
• Helps in writing
• Helps to minimise the speed or stop a moving vehicle by applying brakes
• Helps in gripping objects
If an object started moving in the absence of friction, it would never stop on its own.
Following are the ways to reduce friction:
• Polishing the surface in contact
• Lubrication between the surfaces
• Use of ball bearing/roller bearings that change sliding to rolling friction
• Streamlining the shape of objects that are moving through fluids
Following are the ways to increase friction:
• Make the contact surfaces rough
• Increase the weight of the moving body
• Using soft materials
• Remove lubricating substances from the contact surfaces
Friction is very important force that helps us in various activities despite showing some ill effects. We would not be able to move or stop without friction. We would not be able to grip an object, fix a nail on the wall or tie a knot without friction. That is why it is called a necessary evil.
Following are the disadvantages of friction:
• Reduces the speed of moving objects
• Generates heat
• Causes wear and tear of the objects subject to friction
• Reduces the efficiency of machines