{"id":1369,"date":"2023-03-22T17:06:48","date_gmt":"2023-03-22T17:06:48","guid":{"rendered":"https:\/\/vartmaaninstitutesirsa.com\/?page_id=1369"},"modified":"2024-06-30T04:08:04","modified_gmt":"2024-06-30T04:08:04","slug":"chapter-8-force-and-laws-of-motion","status":"publish","type":"page","link":"https:\/\/vartmaaninstitutesirsa.com\/index.php\/chapter-8-force-and-laws-of-motion\/","title":{"rendered":"Chapter 8 Force and Laws of Motion"},"content":{"rendered":"\r\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 <\/strong>Force<\/strong> and<\/strong> Laws<\/strong> of<\/strong> Motion<\/strong><\/h1>\r\n\r\n
\r\n
\r\n

\u00a0<\/p>\r\n

\"C:\\Users\\dell\\Desktop\\VATMAAN\u00a0 \u00a0<\/em><\/strong>SANDEEP SONI\u2019S PHYSICS<\/span><\/strong>\u00a0<\/span><\/strong>COMPETITION CLASSES<\/span><\/strong>\u00a0\u00a0<\/sub><\/span><\/strong><\/p>\r\n

\u00a0 \u00a0 <\/span><\/strong>(10+1, 10+2, IIT-JEE<\/span><\/strong>\u00a0(<\/span>Main & Advance<\/span>),<\/span>\u00a0NEET, B.Sc.\u00a0<\/span><\/strong>Agriculture<\/span>,\u00a0<\/span>NDA)\u00a0<\/span><\/strong><\/p>\r\n

\u00a0\u00a0\u00a0 <\/span><\/strong>OPP: JHUNTHARA DHARAMSHALA\u00a0<\/span>NEAR SURKHAB<\/span>\u00a0CHOWK,\u00a0<\/span>HISSAR ROAD SIRSA<\/span>\u00a0<\/span><\/p>\r\n

\"\"<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/span>MOTION<\/span><\/u><\/strong>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/strong>PH-\u00a0<\/span>94676-12340, 94164-33457<\/span><\/strong>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/p>\r\n<\/div>\r\n

Chapter -9<\/span><\/strong>\u00a0\u00a0<\/span><\/strong>Force<\/span><\/strong>\u00a0\u00a0<\/span><\/strong>&<\/span><\/strong>\u00a0\u00a0<\/span><\/strong>Laws of Motion<\/span><\/strong><\/p>\r\n

\u00a0\u00a0\u00a0<\/span><\/strong>1.<\/span><\/u><\/strong>\u00a0\u00a0\u00a0<\/span><\/u><\/strong>Force:<\/span><\/u><\/strong><\/p>\r\n

Force may be defined as a pull or push which changes or tends to changes the state of rest or state of motion of a body.<\/span><\/em><\/p>\r\n

\u2022<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>If force is applied directly on a body then force is called\u00a0<\/span>contact force\u00a0<\/span><\/u>and if force is applied without actual contact from a distance then it is called\u00a0<\/span>action at a distance<\/span><\/u>.<\/span><\/p>\r\n

\"https:\/\/study.com\/cimages\/videopreview\/nhalch8yf8.jpg\"<\/p>\r\n

\u00a0\u00a0\u00a0<\/span><\/strong>2.<\/span><\/u><\/strong>\u00a0\u00a0<\/span><\/u><\/strong>Effect Produced By<\/span><\/u><\/strong>\u00a0\u00a0<\/span><\/u><\/strong>Force:<\/span><\/u><\/strong><\/p>\r\n

    \r\n
  1. Force can change speed of an object:-\u00a0<\/em><\/strong><\/li>\r\n<\/ol>\r\n

    \u00a0<\/span>e.g.:- A ball thrown with a larger force will have larger speed and force<\/span>\u00a0\u00a0<\/span>applied on breaks of a car makes car speed slow down.<\/span><\/p>\r\n

      \r\n
    1. Force can change direction of motion of an object:-<\/em><\/strong><\/li>\r\n<\/ol>\r\n

      e.g.:- Force applied on the steering wheel of a car changes the direction of motion of car.<\/span><\/p>\r\n

        \r\n
      1. Force can change the shape of an object:-<\/em><\/strong><\/li>\r\n<\/ol>\r\n

        \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>e.g.:- By pushing the rubber ball we can change its shape.\u00a0<\/span><\/p>\r\n

        Balanced forces & unbalanced forces<\/span><\/strong><\/p>\r\n

        \u2022<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>Balanced forces:<\/span><\/strong>\u00a0<\/span><\/p>\r\n

        Forces are said to be balanced forces if they cancel one another and their resultant force is zero.<\/span><\/p>\r\n

        \u2022<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>Unbalanced forces:<\/span><\/strong>\u00a0<\/span><\/p>\r\n

        When two opposite forces acting on a body, move a body in the direction of the greater force or forces which brings motion in a body are called as unbalanced forces.\u00a0<\/span><\/p>\r\n

        \u00a0<\/span><\/p>\r\n

        \"https:\/\/tse1.mm.bing.net\/th?id=OIP.PyAdUfqaSCdlKTBgcBT77wHaFj&pid=Api&P=0&w=235&h=176\"<\/p>\r\n

        \u00a0<\/span><\/p>\r\n

          \r\n
        1. Aristotle\u2019s Fallacy:<\/span><\/u>\u00a0<\/u><\/li>\r\n<\/ol>\r\n

          According to Aristotle\u2019s Law of motion, an external force is necessary to keep a body moving with uniform velocity i.e. according to this law a body will not remains in motion without a external force. This was proved wrong by Galileo law of inertia.<\/span><\/p>\r\n

            \r\n
          1. Galileo\u2019s Law of Inertia<\/u><\/strong>:<\/u><\/em><\/strong><\/li>\r\n<\/ol>\r\n

            On the basis of a series of experiment performed by Galileo, he gave the law of inertia. According to this law, it is inability of a body to change the state of rest or uniform motion of a body without the help of any external force.<\/span><\/p>\r\n

            Question: 2 how is the inertia of a body measured?<\/span><\/strong><\/p>\r\n

            Inertia of a body is measured by the mass of the body; greater is the amount of mass greater is the inertia of the body. e.g.:- It is easy to change the position of football than a stone of same size because the mass of football is smaller than the mass of the stone. It does not depend on the shape of the body.<\/span><\/p>\r\n

            Inertia:<\/span><\/u><\/strong>\u00a0<\/span>
            The inability of a material body by virtue of which it cannot change its state of rest or uniform motion is called inertia. Inertia means resistance to change.<\/span><\/p>\r\n

            Question:<\/span><\/strong>\u00a0\u00a0<\/span><\/strong>Which of the following has more inertia:<\/span><\/strong>
            (a) a rubber ball and a stone of the same size?<\/span><\/strong>
            (b) a bicycle and a train?<\/span><\/strong>
            (c) a five-rupees coin and a one-rupee coin?<\/span><\/strong>
            Answer:<\/span><\/strong>
            (a) A stone of the same size<\/span>
            (b) a train<\/span>
            (c) a five-rupees coin<\/span>
            As the mass of an object is a measure of its inertia, objects with more mass have more inertia.\u00a0<\/span><\/p>\r\n

            Different Types of Inertia:<\/span><\/u><\/strong><\/p>\r\n

            1. Inertia of rest<\/span><\/strong><\/p>\r\n

            2.<\/span><\/em><\/strong>\u00a0\u00a0<\/span><\/em><\/strong>Inertia of motion<\/span><\/strong><\/p>\r\n

            3.<\/span><\/strong>\u00a0\u00a0<\/span><\/strong>Inertia of direction<\/span><\/strong>\u00a0<\/span><\/p>\r\n

            1. Inertia of rest:<\/span><\/strong>\u00a0<\/span><\/em><\/strong><\/p>\r\n

            The inability of a body changes its state of rest called inertia of rest:-\u00a0<\/span><\/p>\r\n

            Why a person falls backward when bus suddenly starts moving forward?<\/span><\/u>\u00a0<\/span><\/p>\r\n

            when bus starts moving forward then the lower part of the body starts moving forward while the upper part is in rest due to this the person falls backward.\u00a0<\/span><\/p>\r\n

            Question . Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.<\/span><\/strong>
            Answer:<\/span><\/strong>\u00a0<\/span>When the tree\u2019s branch is shaken vigorously the branch attains motion but the leaves stay at rest. Due to the inertia of rest, the leaves tend to remain in its position and hence detaches from the tree to fall down.\u00a0<\/span><\/p>\r\n

            2.Inertia of motion<\/span><\/u><\/strong><\/p>\r\n

            The inability of a body changes its state of rest motion is called inertia of motion:-<\/span><\/p>\r\n

            \u2022<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>Why a person falls backward when bus suddenly stops.<\/span><\/u>\u00a0<\/span><\/p>\r\n

            This is due reason that when bus, suddenly stops then lower part of the body comes into rest while<\/span>\u00a0\u00a0<\/span>the upper part is still in the motion due to this person falls forward.\u00a0<\/span><\/p>\r\n

            Question 4. Explain why it is dangerous to jump out of a moving bus.<\/span><\/strong><\/p>\r\n

            Answer:<\/span><\/strong>\u00a0<\/span>While moving in a bus our body is in motion. On jumping out of a moving bus our feet touches the ground and come to rest. While the upper part of our body stays in motion and moves forward due to inertia of motion and hence we can fall in forward direction.<\/span>
            Hence, to avoid this we need to run forward in the direction of bus.\u00a0<\/span><\/p>\r\n

            3. Inertia of direction<\/span><\/strong><\/p>\r\n

            The inability of a body changes itself its direction of motion is called inertia of direction\u00a0<\/span><\/em><\/p>\r\n

            Q. Why a person sitting inside the bus experience force acting away from the center of curved path when a bus takes a sharp turn?<\/span><\/strong><\/p>\r\n

            Ans. This is due to reason that the body of person does not like to change its direction of motion.<\/span><\/p>\r\n

            Question:<\/span><\/strong>\u00a0\u00a0<\/span><\/strong>how is the inertia of a body measured?<\/span><\/strong>\u00a0\u00a0<\/span>Inertia of a body is measured by the mass of the body; greater is the amount of mass greater is the inertia of the body.<\/span><\/em><\/strong><\/p>\r\n

            \u00a0<\/span>e.g.:- It is easy to change the position of football than a stone of same size because the mass of football is smaller than the mass of the stone. It does not depend on the shape of the body.<\/span><\/p>\r\n

            Momentum<\/span><\/u><\/strong><\/p>\r\n

            The quantity of motion possessed by the body is called the momentum. It is equal to product of mass and velocity of the body.<\/span><\/p>\r\n

            \u00a0\u00a0\u00a0<\/span>Or<\/span>\u00a0\u00a0\u00a0\u00a0<\/span>\"\"\u00a0<\/span><\/p>\r\n

            \u00a0<\/span>\u00a0<\/span>Or\u00a0<\/span>\u00a0<\/span>\u00a0<\/span>\"\"<\/p>\r\n

            Momentum is vector quantity. Its direction is same as that of velocity. The\u00a0<\/span>S.I<\/span><\/em>. unit of momentum =\u00a0<\/span>\"\"\u00a0<\/span>\"\".<\/span><\/p>\r\n

            \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/em><\/strong>Different cases of Momentum:<\/span><\/u><\/em><\/strong><\/p>\r\n

              \r\n
            1. when two object each of mass \"\"\u00a0moves with velocity \"\"and \"\"\u00a0such that \"\"\u00a0then<\/li>\r\n<\/ol>\r\n

              \"\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/p>\r\n

              \"\"\u00a0Or<\/span>\u00a0<\/span>\u00a0<\/span>\"\"<\/p>\r\n

              As<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>\"\"<\/p>\r\n

              Hence equal massive bodies having larger velocity will have larger momentum.<\/span><\/p>\r\n

                \r\n
              1. \"https:\/\/lh3.googleusercontent.com\/proxy\/BF4wdXalH7lDtVpfntpNhPbwm1sI676Z_uYyP5oORRKvq-qiriMHN1N8_Q8Da8QR2OVn6vx6UpX1ki02MIF4-s23cDYEVyI8895j0f5R0VemAuJZPsU\"<\/li>\r\n<\/ol>\r\n

                 <\/p>\r\n

                 <\/p>\r\n

                 <\/p>\r\n

                When two objects of masses \"\"\u00a0such that \"\"\u00a0moves with same velocity then\"\"<\/p>\r\n

                \"\"\u00a0<\/span>\"\"<\/p>\r\n

                As<\/span>\u00a0\u00a0\u00a0<\/span>\"\"<\/p>\r\n

                \"\"Hence the two bodies having same velocities will have larger momentum which have larger mass.<\/span><\/p>\r\n

                  \r\n
                1. When two bodies have equal linear momentum<\/li>\r\n<\/ol>\r\n

                  Then\u00a0\u00a0<\/span>\"\"\u00a0 \u00a0\u00a0<\/span><\/p>\r\n

                  Or<\/span>\u00a0\u00a0\u00a0<\/span>\"\"<\/p>\r\n

                  Or\u00a0<\/span>\u00a0<\/span>\"\"<\/p>\r\n

                  If<\/span>\u00a0\u00a0\u00a0<\/span>\"\"<\/p>\r\n

                  Thus velocities of the bodies are inversely proportional to masses of the bodies i.e. heavier body will have smaller velocity and smaller body will have larger velocity.<\/span><\/p>\r\n

                  How much momentum will a dumb-bell of mass 10 kg transfer to the floor if it falls from a height of 80 cm? Take its downward acceleration to be 10 ms<\/span><\/strong>-2<\/sup><\/span><\/strong>.<\/span><\/strong>\u00a0<\/span><\/p>\r\n

                  Ans:<\/span>\u00a0\u00a0\u00a0<\/span>m=10kg ,<\/span>\u00a0\u00a0<\/span>h=80cm= 0.8m , a= 10m\/s^2<\/span>\u00a0\u00a0<\/span>, u=0\u00a0<\/span><\/p>\r\n

                  \"\"<\/p>\r\n

                  \"\"<\/p>\r\n

                  \"\"<\/p>\r\n

                  \"\"<\/p>\r\n

                  Momentum\u00a0<\/span>\"\"<\/p>\r\n

                  Newton\u2019s Laws of Motion<\/span><\/u><\/strong><\/p>\r\n

                  Newton\u2019s First Law of Motion<\/span><\/strong>:<\/span><\/em><\/strong>\u00a0<\/span><\/p>\r\n

                  A body in rest will remain in rest or a body is in motion will remain in motion till any external force is applied on the body.<\/span><\/em><\/p>\r\n

                  How Newton\u2019s first law defines force?<\/span><\/u><\/em>\u00a0<\/span><\/p>\r\n

                  \u2022<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>According to Newton\u2019s first law, force is external agency which changes the state of rest or uniform motion of the body. Hence this law gives the qualitative definition of force.<\/span><\/p>\r\n

                  \u2022<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>Newton\u2019s first law sometimes called law of inertia.<\/span><\/p>\r\n

                  Question Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet?<\/span><\/strong>\u00a0<\/span><\/p>\r\n

                  \"\"<\/p>\r\n

                   <\/p>\r\n

                   <\/p>\r\n

                   <\/p>\r\n

                  As the wooden cabinet moves across the floor at a constant velocity and the force applied is 200 N. Hence the frictional force that will be exerted on the cabinet will be less than 200 N.<\/span>\u00a0<\/span><\/strong><\/p>\r\n

                  Newton\u2019s Laws of Motion<\/span><\/u><\/strong><\/p>\r\n

                  Newton\u2019s First Law of Motion<\/span><\/strong>:<\/span><\/em><\/strong>\u00a0<\/span><\/p>\r\n

                  A body in rest will remain in rest or a body is in motion will remain in motion till any external force is applied on the body.<\/span><\/em><\/p>\r\n

                  How Newton\u2019s first law defines force?<\/span><\/u><\/em>\u00a0<\/span><\/p>\r\n

                  \u2022<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>According to Newton\u2019s first law, force is external agency which changes the state of rest or uniform motion of the body. Hence this law gives the qualitative definition of force.<\/span><\/p>\r\n

                  \u2022<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>Newton\u2019s first law sometimes called law of inertia.<\/span><\/p>\r\n

                  Newton\u2019s Second Law of Motion:\u00a0<\/span><\/strong><\/p>\r\n

                  According to Newton\u2019s second law of motion, the rate of change of linear momentum is directly proportional to applied force.<\/span><\/em><\/p>\r\n

                  Mathematically<\/span><\/p>\r\n

                  \"\"<\/p>\r\n

                  or\u00a0<\/span> \"\"\u00a0\u00a0<\/span> (<\/span>\"\")<\/span><\/p>\r\n

                  Or\u00a0<\/span> \"\"<\/p>\r\n

                  Or\u00a0<\/span> \"\"<\/p>\r\n

                  Or\u00a0<\/span> \"\"<\/p>\r\n

                  Where<\/span> \"\"<\/p>\r\n

                  \"\"\u00a0<\/span> \"\"<\/p>\r\n

                  Force is a vector quantity. Its dimensional formula is\u00a0<\/span>\"\"<\/p>\r\n

                  Unit of Force:<\/span><\/u><\/strong>\u00a0<\/span><\/u><\/em><\/strong><\/p>\r\n

                  There are two types of unit of Force<\/span><\/em><\/p>\r\n

                    \r\n
                  1. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/span>\u00a0 \u00a0 \u00a0 Absolute Unit of Force:<\/li>\r\n<\/ol>\r\n

                    \u00a0<\/span>An absolute unit of force is defined as the force which produces unit acceleration in unit mass of a body.<\/span><\/p>\r\n

                    In S.I. absolute unit of force is Newton<\/span><\/p>\r\n

                    \u00a0(<\/span>\"\")<\/span><\/p>\r\n

                    \u00a0<\/span>In\u00a0<\/span>\"\"absolute unit of force is dyne (1 dyne<\/span>\"\")<\/span><\/p>\r\n

                      \r\n
                    1. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/span>\u00a0 \u00a0 \u00a0Gravitational Units of Force<\/span>:<\/li>\r\n<\/ol>\r\n

                      A gravitational unit of force is defined as the force which produces\u00a0<\/span>\"\"\u00a0\u00a0<\/span>(acceleration on due to gravity) acceleration in a body of unit mass.<\/span><\/p>\r\n

                      In S.I. the gravitational unit of force is Kilogram weight\u00a0<\/span>\"\"\u00a0or Kilogram force\u00a0<\/span>\"\"\"\"<\/p>\r\n

                      In\u00a0<\/span>\"\"\u00a0the gravitational unit of force is gram weight\u00a0<\/span>\"\"\u00a0or gram force\u00a0<\/span>\"\"<\/p>\r\n

                      \"\"<\/p>\r\n

                      Relation between Newton and dyne<\/span><\/p>\r\n

                      \"\"<\/p>\r\n

                      Or\u00a0<\/span> \"\"<\/p>\r\n

                      Difference between Gravitational unit and absolute unit of force:<\/span><\/strong><\/p>\r\n

                      \uf0fc<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>The absolute units of force remains the same throughout the universe but the Gravitational unit depends upon\u00a0<\/span>\"\"\u00a0so changes from place to place.<\/span><\/p>\r\n

                      \uf0fc<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>A gravitational unit is\u00a0<\/span>\"\"\u00a0times the corresponding absolute unit. Gravitational unit is also called weight or practical unit of force.<\/span><\/p>\r\n

                      Question.<\/span><\/strong>\u00a0\u00a0<\/span><\/strong>An automobile vehicle has a mass of 1500 kg. What must be the force between the vehicle and road if the vehicle is to be stopped with a negative acceleration of 1.7 ms<\/span><\/strong>-2<\/sup><\/span><\/strong>?<\/span><\/strong>\u00a0<\/span><\/p>\r\n

                      Ans:\u00a0<\/span>\"\"\u00a0,\u00a0<\/span>\"\"\u00a0\u00a0<\/span>,\u00a0<\/span>\"\"\u00a0\u00a0\u00a0<\/span><\/p>\r\n

                      \u00a0<\/span>\"\"<\/p>\r\n

                      The force between the vehicle and road is <\/span><\/p>\r\n

                      =-2550N<\/span><\/p>\r\n

                      Question . A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 tones (Hint : 1 tone = 1000 kg).<\/span><\/strong>\u00a0<\/span><\/p>\r\n

                      Ans:\u00a0<\/span>\"\"\u00a0\u00a0\u00a0\u00a0<\/span>\"\"\u00a0,<\/span><\/p>\r\n

                      \u00a0\u00a0\u00a0\u00a0<\/span>\"\"\u00a0\u00a0\u00a0<\/span>\"\"\u00a0,\u00a0<\/span>\"\"\u00a0<\/span>\"\"<\/p>\r\n

                      \"\"<\/p>\r\n

                      \"\"<\/p>\r\n

                      \"\"\u00a0\u00a0\u00a0<\/span>\"\"<\/p>\r\n

                      \"\"\u00a0<\/span><\/p>\r\n

                      Question.<\/span><\/strong>\u00a0\u00a0<\/span><\/strong>A stone of 1kg is thrown with a velocity of 20 ms~1 across the frozen surface of a lake and comes to rest after travelling a distance of 50 m. What is the force of friction between the stone and the ice?<\/span><\/strong>\u00a0<\/span><\/p>\r\n

                      Ans:\u00a0<\/span>\"\"\u00a0\u00a0\u00a0\u00a0<\/span>\"\"\u00a0,<\/span>\u00a0\u00a0\u00a0<\/span><\/p>\r\n

                      \u00a0<\/span>\"\"\u00a0\u00a0\u00a0<\/span>\"\"\u00a0,\u00a0<\/span>\"\"\u00a0<\/span>\"\"<\/p>\r\n

                      \"\"<\/p>\r\n

                      \"\"<\/p>\r\n

                      So<\/span>\u00a0\u00a0<\/span>\"\"<\/p>\r\n

                      \"\"\u00a0<\/span><\/p>\r\n

                      \"\"<\/p>\r\n

                        \r\n
                      1. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/span>\u00a0 \u00a0 Newton\u2019s Third Law of Motion:<\/li>\r\n<\/ol>\r\n

                        It states that to every action, there is always an equal and opposite reaction.<\/span><\/p>\r\n


                        <\/span>Suppose\u00a0<\/span>\"\"\u00a0is the amount of force exerted by body<\/span>\u00a0\u00a0<\/span>\"\"\u00a0on body<\/span><\/p>\r\n

                        \u00a0<\/span>\"\"\u00a0Is the amount of force on\u00a0<\/span>\"\"\u00a0\u00a0<\/span>due to\u00a0<\/span>\"\"\u00a0<\/span><\/p>\r\n

                        then from Newton\u2019s <\/span>Third law of motion<\/span><\/p>\r\n

                        \u00a0\u00a0\u00a0<\/span>\"\"<\/p>\r\n

                        I.e. Force on\u00a0<\/span>\"\"<\/p>\r\n

                        e.g.: During swimming a person pushes water back word then the water pushes person in forward direction.<\/span><\/p>\r\n

                        \uf0d8<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>Here Newton\u2019s third law shows that a single force cannot exist in nature, the force exists in pairs.<\/span><\/p>\r\n

                        \uf0d8<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>Newton\u2019s third law of motion is applicable irrespective of the nature of the forces.<\/span><\/p>\r\n

                        \uf0d8<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>Action and reaction always acts on the different bodies.<\/span><\/p>\r\n

                        \uf0d8<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>The force of action and reaction cannot cancel each other because act on different bodies.<\/span><\/p>\r\n

                        \uf0d8<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>No action act occurs in the absence of reaction.<\/span><\/p>\r\n

                        Illustrations of Newton\u2019s Third Law of Motion:<\/span><\/strong><\/p>\r\n