Question

A vector `vec(B)` which has a magnitude 8.0 is added to a vector `vec(A)` which lies along the x-axis. The sum of these two vector is a third vector which lies along the y-axis and has a magnitude that is twice the magnitude of `vec(A)`. Find the magnitude of `vec(A)`
A. `(6)/sqrt(5)`
B. `(8)/sqrt(5)`
C. `(12)/sqrt(5)`
D. `(16)/sqrt(5)`

Answer 1

Correct Answer - B
`|vecQ|=8,vecP+vecQ=vecR`,
`R_(y)=2P_(x),(P_(x)+Q_(x))+Q_(y)=R_(y)`
`Q_(x)^(2)+Q_(y)^(2)=64rArrP_(x)^(2)+4P_(x)^(2)=64`