Page 44 - Physics - XI
P. 44

Sources of Error

              1.  Pulleys may have friction.
              2.  The weights may not be accurate.

              3.  Slight error in marking the point may result in large error.


                                                           VIVA  VOCE


               Q1.  Can vectors be added like scalars? If not, why?
              Ans.  Vectors  cannot  be  added  algebraically  like  scalars  because  vectors  have  magnitude  as  well  as
                     direction, but scalars have only magnitude. Simply a change in direction changes the value of the
                     vector quantity.

               Q2.  Can the parallelogram law of vector addition be used to add forces and velocities?
              Ans.  Yes, it can be used because forces and velocities are also vectors.

               Q3.  What is the parallelogram law of forces?
              Ans.  If  two  forces  are  represented  both  in  magnitude  and  direction  by  the  two  adjacent  sides  of  a
                     parallelogram passing through a point, their resultant can be represented both in magnitude and
                     direction by the diagonal of the parallelogram passing through the same point.

               Q4.  What do you mean by resolution of a vector?
              Ans.  The splitting of a single vector into its number of components is called resolution of a vector.

               Q5.  How will you add more than two vectors?
              Ans.  By polygon law of vector addition, we can add more than two vectors.

               Q6.  Defi ne force.
              Ans.  It is the push or pull which changes or tends to change the state of rest or of uniform motion of the
                     body in a straight line.

               Q7.  What is the unit of force in S.I. system?
              Ans.  N (newton)

               Q8.  Is force a scalar or a vector quantity?
              Ans.  Force is a vector quantity.

               Q9.  What do you mean by a resultant force?
              Ans.  When a number of forces are acting simultaneously on the body, they can be replaced by a single
                     force having the same eff ect. This single force is called a resultant force.

               Q10.  What are scalar and vector quantities?
              Ans.  The quantities which require both magnitude and direction for their description are called vector
                     quantities while scalars have only magnitude.

               Q11.  What do you mean by the term equilibrium?
              Ans.  When the resultant of all the forces acting on a body is zero and it produces no acceleration in the
                     body, the body is said to be in equilibrium.







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