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?

Explanation

`B = (7.0i - 3.0j ) xx 10 ^(-3) T
` a = acceleration
` = (i + 7j ) xx10 ^(-6) m//s ^ 2 `
Let the gap be x
Since B and a are always perpendicular ,
` B a = 0`
rArr 7x xx 10^(-3) xx 10^(-6) - 3 xx 10^(-3) xx 7 xx 10^(-6) =0 `
rArr 7x -21 = 0 `
` x = (21) /(7) = 3 `