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3-1.Vectors
medium
The vector sum of two forces is perpendicular to their vector differences. In that case, the forces
AAre equal to each other in magnitude
BAre not equal to each other in magnitude
CCannot be predicted
DAre equal to each other
(AIPMT-2003) (AIIMS-2012)
Solution
(a) If two vectors are perpendicular then their dot product must be equal to zero. According to problem
$(\overrightarrow A + \overrightarrow B ).(\overrightarrow A – \overrightarrow B ) = 0$
$⇒$$\overrightarrow A .\overrightarrow A – \overrightarrow A .\overrightarrow B + \overrightarrow B .\overrightarrow A – \overrightarrow B .\overrightarrow B = 0$
$⇒$ ${A^2} – {B^2} = 0$
$⇒$ ${A^2} = {B^2}$
$\therefore $ $A = B$ i.e. two vectors are equal to each other in magnitude.
$(\overrightarrow A + \overrightarrow B ).(\overrightarrow A – \overrightarrow B ) = 0$
$⇒$$\overrightarrow A .\overrightarrow A – \overrightarrow A .\overrightarrow B + \overrightarrow B .\overrightarrow A – \overrightarrow B .\overrightarrow B = 0$
$⇒$ ${A^2} – {B^2} = 0$
$⇒$ ${A^2} = {B^2}$
$\therefore $ $A = B$ i.e. two vectors are equal to each other in magnitude.
Standard 11
Physics