Find |\(\vec{p}\)|, if for a unit vector \(\vec{a}\), (\(\vec{p}\)- \(\vec{a}\)).((\(\vec{p}\)+ \(\vec{a}\)) =10
Answer & explanation
Correct answer: option 2
We have (\(\vec{p}\)- \(\vec{a}\)).((\(\vec{p}\)+ \(\vec{a}\)) =10
⇒|\(\vec{p}\)|2 - |\(\vec{a}\)|2 =10
⇒|\(\vec{p}\)|2 - 1 =10 |\(\vec{a}\)|=1 as \(\vec{a}\) is a unit vector)
⇒|\(\vec{p}\)|2 =11
⇒|\(\vec{p}\)|= √11