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3-1.Vectors
medium
The resultant of $\overrightarrow A + \overrightarrow B $ is ${\overrightarrow R _1}.$ On reversing the vector $\overrightarrow {B,} $ the resultant becomes ${\overrightarrow R _2}.$ What is the value of $R_1^2 + R_2^2$
A
${A^2} + {B^2}$
B
${A^2} - {B^2}$
C
$2({A^2} + {B^2})$
D
$2({A^2} - {B^2})$
Solution
(c) ${\vec R_1} = \vec A + \vec B$, ${\vec R_2} = \vec A – \vec B$
$R_1^2 + R_2^2 = {\left( {\sqrt {{A^2} + {B^2}} } \right)^2} + {\left( {\sqrt {{A^2} + {B^2}} } \right)^2}$=$2\left( {{A^2} + {B^2}} \right)$
Standard 11
Physics