An experimenter's diary reads as follows: ''a charged particle is projected in a magnetic feld of `(7.0 veci - 3.0 vecj )X 10^(-3)` T. The acceleraation of the particle is found to be `(sqrare veci +7.0 vec j) X10 ^(-6) ms^(-2)'. The number to the left of `vec i` in the last expression was not readable. What can this number be?

Options

A. `3`
B. `2`
C. `1`
D. zero

Answer

A

Explanation

`vec(B) = (7 hat(i) - 3 hat(j)) xx 10^(-3)T, vec(a) = (lambda hat(i) + 7 hat(j)) xx 10^(-6) m//sec^(2)`
Since `F_(m)` is `_|_^(ar)` to `vec(B)`, therefore `vec(a)` is `_|_^(ar)` to `vec(B)`
The dot product of `_|_^(ar)` vectors is zero
`vec(a).vec(B) = 7 lambda - 21 = 0 rArr lambda = 3`