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

  • question_answer
           Show that the displacement vector does not depend upon the choice of the coordinate axes.

    Answer:

                    Let a particle be displaced from location P to Q. Fig. 2(c).53. So the displacement vector \[=\overset{\to }{\mathop{PQ}}\,=\overset{\to }{\mathop{r}}\,\] With respect to origin O, let, \[(\overset{\to }{\mathop{OP}}\,)=\overset{\to }{\mathop{{{r}_{1}}}}\,\]  and \[(\overset{\to }{\mathop{OQ}}\,)=\overset{\to }{\mathop{{{r}_{2}}}}\,\]. With respect to origin \[O'\], Let                 \[(\overset{\to }{\mathop{O'P}}\,)=\overset{\to }{\mathop{{{r}_{1}}'}}\,\]         and        \[(\overset{\to }{\mathop{O'Q}}\,)=\overset{\to }{\mathop{{{r}_{2}}'}}\,\] Using triangle law of vectors addition, we have                      \[\overset{\to }{\mathop{{{r}_{1}}}}\,+\overset{\to }{\mathop{r}}\,=\overset{\to }{\mathop{{{r}_{2}}}}\,\] or \[\overset{\to }{\mathop{{{r}_{{}}}}}\,=\overset{\to }{\mathop{{{r}_{2}}}}\,-\overset{\to }{\mathop{{{r}_{1}}}}\,\] Also, \[\overset{\to }{\mathop{{{r}_{{}}}}}\,+\overset{\to }{\mathop{{{r}_{1}}}}\,'=\overset{\to }{\mathop{{{r}_{2}}}}\,'\] or  \[\overset{\to }{\mathop{r}}\,=\overset{\to }{\mathop{{{r}_{2}}'}}\,-\overset{\to }{\mathop{{{r}_{1}}'}}\,\] so, \[\overset{\to }{\mathop{r}}\,=\overset{\to }{\mathop{{{r}_{2}}}}\,-\overset{\to }{\mathop{{{r}_{1}}}}\,=\overset{\to }{\mathop{{{r}_{2}}'}}\,-\overset{\to }{\mathop{{{r}_{1}}'}}\,\] This shows that the displacement vector \[\overset{\to }{\mathop{r}}\,\] is independent of the choice of origin.


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