{"id":88837,"date":"2022-02-12T13:26:37","date_gmt":"2022-02-12T07:56:37","guid":{"rendered":"https:\/\/infinitylearn.com\/surge\/?p=88837"},"modified":"2023-06-06T15:50:53","modified_gmt":"2023-06-06T10:20:53","slug":"friction","status":"publish","type":"post","link":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/","title":{"rendered":"Friction"},"content":{"rendered":"

Friction Definition:<\/strong><\/span><\/p>\n

Whenever a body moves or tends to move over the surface of another body, a force comes into play which acts parallel to the surface of contact and opposes the relative motion. This opposing force is called friction.<\/p>\n

It has the following types :<\/strong><\/p>\n

Static friction:<\/span> <\/strong>It is the friction between two surfaces of bodies at rest due to impending motion.<\/p>\n

Nature of static friction:<\/span><\/strong><\/p>\n

    \n
  1. It is a self-acting<\/strong> force. It acts by itself.<\/li>\n
  2. It is a self-adjusting<\/strong> force. It adjusts its magnitude and direction to keep itself always equal and opposite to the horizontal force applied to move the body at rest<\/li>\n
  3. It has a limiting value (maximum value)<\/strong> called limiting friction. The limiting friction is equal to the least force required to move the body from rest.<\/li>\n<\/ol>\n

    Dynamic (or kinetic) friction.<\/strong> <\/span>It is the friction between two surfaces of bodies in motion. It is slightly less than the static friction.<\/p>\n

    Dynamic friction has two types :<\/strong>
    \n(i) Sliding friction. It is the friction in sliding motion.
    \n(ii) Rolling friction. It is the friction in rolling motion.
    \nRolling friction is less than the sliding friction.<\/p>\n

    Origin of friction <\/strong><\/span>
    \nThe following two factors are responsible for the friction :
    \n1. Roughness of surfaces is the cause of friction. The roughness or irregularities of surfaces provide the interlocking between the two surfaces when the surfaces are in relative motion. Interlocking of the elevations and the depressions of the lower surface and bottom surface of the bodies are shown in (Fig. 7.01). When the body is pulled, elevations collide and friction provide.
    \n2. Force of attraction between molecules in the lower surface and bottom surface of the body. It is called adhesive force.
    \n\"friction-1\"<\/p>\n

    Friction is necessary <\/strong><\/span>
    \nFriction plays an important part in daily life. In its absence, many acts may not be able to be performed. They are given below :<\/p>\n

      \n
    1. Without friction, a motion cannot be started. We cannot walk on a friction less surface.<\/li>\n
    2. Without friction, a motion cannot be stopped. Brakes will not work if there is no friction.<\/li>\n
    3. Without friction, a motion cannot be transferred. The belt will not be able to rotate a machine wheel by motor wheel if there is no friction between belt and wheels.<\/li>\n
    4. Without friction, knots will not stay. Packing, tying, bandaging will be difficult.<\/li>\n
    5. Without friction, grinding will not take place. Wheat and spices will not be grinded.<\/li>\n
    6. Without friction, nails will not stay in position. It will be difficult to assemble a furniture item.<\/li>\n
    7. Without friction, match stick will not ignite.<\/li>\n
    8. Without friction, writing on a surface will not be possible.<\/li>\n
    9. Without friction, holding the things will not possible.<\/li>\n
    10. Without friction, eating is not possible etc.<\/li>\n<\/ol>\n

      Friction is evil <\/strong><\/span>
      \nThough friction is useful in many fields, it is harmful (evil) in the followings.
      \n1. Due to friction between different parts of a machine, wear and tear of parts take place and excessive heat is produced. This reduces the life of the machine.
      \n2. Unnecessary, expense of energy to overcome the friction. Hence, output is always less than input.<\/p>\n

      Reduction of friction <\/strong><\/span>
      \nIn cases where friction is taken as an evil, it is desired to reduce it. The friction can be reduced by following methods :<\/p>\n

        \n
      1. Smoothening the surface by rubbing and polishing. Rubbing reduces height of elevations. Polishing fills the reduced depth of depressions. In the absence of elevations and depressions, interlocking reduces. Friction becomes reduced.
        \nBut too much smoothness of surfaces in contact increases friction. It is so because the molecules of the two surfaces come in close contact. Attraction between the molecules increases, which increases friction.<\/li>\n
      2. Lubricating the surfaces in contact by a proper lubricant. Lubricant between two surfaces keeps them separate and prevents interlocking. This reduces friction.
        \nSelection of lubricant must be proper, Grease must be used for heavy bodies, heavy oil must be used for bodies of moderate weight and light oil must be used for light bodies.<\/li>\n
      3. Lining the surfaces or surface with soft material. Hard material surfaces have more friction due to strong forces of attraction between their molecules. (They are hard, be-cause of this strong force). To reduce friction between them, without effecting their strength, they are lined (coated) with soft material. Contact between soft material surfaces experiences less friction.
        \nSteel wheels of trains are lined with lead to reduce friction between them and steel rail track.<\/li>\n
      4. Converting sliding friction into rolling friction. When wheel is mounted direct on axle, surface of wheel hole slides over axle surface as the wheel rolls [Fig. 7.02 (a)]. There is more friction. The motion becomes slow.
        \n\"friction-2\"
        \nBut when balls (ball bearings) are introduced between axle surface and hole surface of wheel, situation becomes different [Fig. 7.02 (6)]. Now when the wheel rolls, balls roll and surface of hole moves over rolling balls. Friction is considerably reduced.
        \nIt is for this reason that all movable heavy bodies are provided with wheels at bottom (examples are hospital bed, stretcher, large-sized suitcases etc.).<\/li>\n
      5. By streamlining. Friction due to air is reduced by streamlining the shape of the body moving through air. For example jets, aeroplanes, fast moving cars etc.<\/li>\n<\/ol>\n

        Incrasing friction <\/strong><\/span>
        \nIn cases where friction is necessary, it is desired to increase it. The friction can be in-creased by following methods (which are reverse of reduction methods).<\/p>\n

          \n
        1. Roughening the surface by chiseling it.<\/li>\n
        2. Sanding the surface.<\/li>\n
        3. Lining with hard material.<\/li>\n
        4. Converting rolling friction into sliding friction.
          \nWhen brakes are applied on a moving vehicle, rolling of wheels stop. Then wheels slide on the road. Due to friction, vehicle stops.<\/li>\n<\/ol>\n

          Laws of limiting friction <\/strong><\/span>
          \nThere are four laws of limiting friction. They are stated below :<\/p>\n

            \n
          1. First Law (law for direction). Limiting friction acts tangential to the surfaces in contact, in backward direction (i.e., opposite to direction of motion).<\/li>\n
          2. Second Law (law for magnitude). Limiting friction is directly proportional to the normal reaction acting on the body.
            \n\"friction-3\"<\/li>\n
          3. Third Law (law of dependence). Limiting friction depends upon the nature (rough or polished) and the material (hard or soft) of the surfaces in contact.<\/li>\n
          4. Fourth Law (law for independence). Limiting friction is independent of the area and the shape of the surfaces in contact.<\/li>\n<\/ol>\n

            Coefficient of friction <\/strong><\/span>
            \nDefinition. The limiting friction is directly proportional to the normal reaction. If F be the limiting friction and R be the normal reaction, then
            \n\u03bc =F\/R
            \nF=\u03bc R
            \nHere \u03bc is called coefficient of friction, \u03bc does not has unit and dimensions because it is the ratio, of two like physical quantities.<\/p>\n

            Angle of friction <\/strong><\/span>
            \nDefinition. It is the angle that the resultant of limiting friction an<J normal reaction makes with the normal reaction. It is shown by \u03b8 in diagram.
            \n\"angle<\/p>\n

            Angle of sliding or angle of repose <\/strong><\/span>
            \nDefinition. It is the angle of inclination of a rough surface with horizontal, such that a body kept over it, just starts to sliding down.
            \nRelation. Figure 7.04 shows a body of mass m and weight mg kept on a surface inclined at an angle \u03b8 with horizontal.
            \n\"angle
            \nForces acting on the body are also shown in the diagram (Fig. 7.04).
            \nWhen body just starts to sliding down,
            \nFor equilibrium along inclined plane, mg sin \u03b8 = F (limiting friction)
            \nFor equilibrium along normal to inclined plane, mg,cos \u03b8 = R (normal reaction)
            \n\"friction-6\"
            \nor tan \u03b8 = \u03bc
            \nHence, tangent of angle of repose is equals to the coefficient of static friction.
            \n(c) Application. Using an inclined plane with variable angle of inclination, coefficient of friction can be determined.<\/p>\n","protected":false},"excerpt":{"rendered":"

            Friction Definition: Whenever a body moves or tends to move over the surface of another body, a force comes into […]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_focuskw":"Friction Definition","_yoast_wpseo_title":"Friction - Definition, Types of Friction | class 11 pdf Notes","_yoast_wpseo_metadesc":"When a body moves or tends to move over another body's surface, a force arises that opposes the relative motion, acting parallel to surface.","custom_permalink":"study-material\/physics\/friction\/"},"categories":[4,21],"tags":[],"table_tags":[],"acf":[],"yoast_head":"\nFriction - Definition, Types of Friction | class 11 pdf Notes<\/title>\n<meta name=\"description\" content=\"When a body moves or tends to move over another body's surface, a force arises that opposes the relative motion, acting parallel to surface.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Friction - Definition, Types of Friction | class 11 pdf Notes\" \/>\n<meta property=\"og:description\" content=\"When a body moves or tends to move over another body's surface, a force arises that opposes the relative motion, acting parallel to surface.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/\" \/>\n<meta property=\"og:site_name\" content=\"Infinity Learn by Sri Chaitanya\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/InfinityLearn.SriChaitanya\/\" \/>\n<meta property=\"article:published_time\" content=\"2022-02-12T07:56:37+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2023-06-06T10:20:53+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2022\/02\/31063917772_234cac75ba_o.png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@InfinityLearn_\" \/>\n<meta name=\"twitter:site\" content=\"@InfinityLearn_\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Prasad Gupta\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"7 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Friction - Definition, Types of Friction | class 11 pdf Notes","description":"When a body moves or tends to move over another body's surface, a force arises that opposes the relative motion, acting parallel to surface.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/","og_locale":"en_US","og_type":"article","og_title":"Friction - Definition, Types of Friction | class 11 pdf Notes","og_description":"When a body moves or tends to move over another body's surface, a force arises that opposes the relative motion, acting parallel to surface.","og_url":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/","og_site_name":"Infinity Learn by Sri Chaitanya","article_publisher":"https:\/\/www.facebook.com\/InfinityLearn.SriChaitanya\/","article_published_time":"2022-02-12T07:56:37+00:00","article_modified_time":"2023-06-06T10:20:53+00:00","og_image":[{"url":"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2022\/02\/31063917772_234cac75ba_o.png"}],"twitter_card":"summary_large_image","twitter_creator":"@InfinityLearn_","twitter_site":"@InfinityLearn_","twitter_misc":{"Written by":"Prasad Gupta","Est. reading time":"7 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Organization","@id":"https:\/\/infinitylearn.com\/surge\/#organization","name":"Infinity Learn","url":"https:\/\/infinitylearn.com\/surge\/","sameAs":["https:\/\/www.facebook.com\/InfinityLearn.SriChaitanya\/","https:\/\/www.instagram.com\/infinitylearn_by_srichaitanya\/","https:\/\/www.linkedin.com\/company\/infinity-learn-by-sri-chaitanya\/","https:\/\/www.youtube.com\/c\/InfinityLearnEdu","https:\/\/twitter.com\/InfinityLearn_"],"logo":{"@type":"ImageObject","@id":"https:\/\/infinitylearn.com\/surge\/#logo","inLanguage":"en-US","url":"","contentUrl":"","caption":"Infinity Learn"},"image":{"@id":"https:\/\/infinitylearn.com\/surge\/#logo"}},{"@type":"WebSite","@id":"https:\/\/infinitylearn.com\/surge\/#website","url":"https:\/\/infinitylearn.com\/surge\/","name":"Infinity Learn by Sri Chaitanya","description":"Surge","publisher":{"@id":"https:\/\/infinitylearn.com\/surge\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/infinitylearn.com\/surge\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"en-US"},{"@type":"ImageObject","@id":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/#primaryimage","inLanguage":"en-US","url":"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2022\/02\/31063917772_234cac75ba_o.png?v=1643698718","contentUrl":"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2022\/02\/31063917772_234cac75ba_o.png?v=1643698718","width":501,"height":341},{"@type":"WebPage","@id":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/#webpage","url":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/","name":"Friction - Definition, Types of Friction | class 11 pdf Notes","isPartOf":{"@id":"https:\/\/infinitylearn.com\/surge\/#website"},"primaryImageOfPage":{"@id":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/#primaryimage"},"datePublished":"2022-02-12T07:56:37+00:00","dateModified":"2023-06-06T10:20:53+00:00","description":"When a body moves or tends to move over another body's surface, a force arises that opposes the relative motion, acting parallel to surface.","breadcrumb":{"@id":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/infinitylearn.com\/surge\/"},{"@type":"ListItem","position":2,"name":"Friction"}]},{"@type":"Article","@id":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/#article","isPartOf":{"@id":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/#webpage"},"author":{"@id":"https:\/\/infinitylearn.com\/surge\/#\/schema\/person\/143c89c9c2f5e56ed91f96dde47b0b05"},"headline":"Friction","datePublished":"2022-02-12T07:56:37+00:00","dateModified":"2023-06-06T10:20:53+00:00","mainEntityOfPage":{"@id":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/#webpage"},"wordCount":1221,"publisher":{"@id":"https:\/\/infinitylearn.com\/surge\/#organization"},"image":{"@id":"https:\/\/infinitylearn.com\/surge\/study-material\/physics\/friction\/#primaryimage"},"thumbnailUrl":"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2022\/02\/31063917772_234cac75ba_o.png","articleSection":["Physics","Study Materials"],"inLanguage":"en-US"},{"@type":"Person","@id":"https:\/\/infinitylearn.com\/surge\/#\/schema\/person\/143c89c9c2f5e56ed91f96dde47b0b05","name":"Prasad Gupta","image":{"@type":"ImageObject","@id":"https:\/\/infinitylearn.com\/surge\/#personlogo","inLanguage":"en-US","url":"https:\/\/secure.gravatar.com\/avatar\/200104b443e586c76c46cadc113d931c?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/200104b443e586c76c46cadc113d931c?s=96&d=mm&r=g","caption":"Prasad Gupta"},"url":"https:\/\/infinitylearn.com\/surge\/author\/prasad\/"}]}},"_links":{"self":[{"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/posts\/88837"}],"collection":[{"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/comments?post=88837"}],"version-history":[{"count":0,"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/posts\/88837\/revisions"}],"wp:attachment":[{"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/media?parent=88837"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/categories?post=88837"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/tags?post=88837"},{"taxonomy":"table_tags","embeddable":true,"href":"https:\/\/infinitylearn.com\/surge\/wp-json\/wp\/v2\/table_tags?post=88837"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}