11th Class Physics Motion in a Straight Line / सरल रेखा में गति Question Bank 11th CBSE Physics One Dimensional Motion

  • question_answer
    If \[\overset{\to }{\mathop{\text{A}}}\,.\overset{\to }{\mathop{\text{B}}}\,=\overset{\to }{\mathop{\text{A}}}\,.\overset{\to }{\mathop{C}}\,\],is it correct to conclude that \[\overset{\to }{\mathop{\text{B}}}\,=\overset{\to }{\mathop{C}}\,\,\,?\]

    Answer:

                    Given \[\overset{\to }{\mathop{\text{A}}}\,.\overset{\to }{\mathop{\text{B}}}\,=\overset{\to }{\mathop{\text{A}}}\,.\overset{\to }{\mathop{C}}\,\], i.e., \[AB\,\cos {{\text{ }\!\!\theta\!\!\text{ }}_{\text{1}}}=AC\ \cos {{\text{ }\!\!\theta\!\!\text{ }}_{\text{2}}}\]                                                       ?? (i)                 Where \[{{\text{ }\!\!\theta\!\!\text{ }}_{\text{1}}}\]is smaller angle between \[\overset{\to }{\mathop{\text{A}}}\,\]and\[\overset{\to }{\mathop{B}}\,\]; and\[{{\text{ }\!\!\theta\!\!\text{ }}_{\text{2}}}\] is the smaller angle between \[\overset{\to }{\mathop{\text{A}}}\,\]and\[\overset{\to }{\mathop{C}}\,\] .                 From (i), \[\text{B}\,\cos {{\text{ }\!\!\theta\!\!\text{ }}_{\text{1}}}=\text{C}\ \cos {{\text{ }\!\!\theta\!\!\text{ }}_{\text{2}}}\]                                                                                 ?? (ii) If \[{{\text{ }\!\!\theta\!\!\text{ }}_{\text{1}}}={{\text{ }\!\!\theta\!\!\text{ }}_{\text{2}}}\], then from (ii), \[\text{B}\,=C\]or \[\overset{\to }{\mathop{\text{B}}}\,\,=\overset{\to }{\mathop{\text{C}}}\,\] If \[{{\text{ }\!\!\theta\!\!\text{ }}_{\text{1}}}\ne {{\text{ }\!\!\theta\!\!\text{ }}_{\text{2}}}\],then from (ii), \[\text{B}\,\ne C\] or \[\overset{\to }{\mathop{\text{B}}}\,\,\,\ne \overset{\to }{\mathop{C}}\,\]


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