Question

An experimenters diary reads as follows : A charged particle is projected in a magnetic field $(7\hat{i}-3\hat{j})\times {10}^{-3}$T . The acceleration of the particle is found to be $(\hat{i}+7\hat{j})\times {10}^{-6}m{s}^{-2}$ then coefficient of $\hat{i}$ is

• A. $3.0$
• B. $7.0$
• C. $5.0$
• D. $4.0$

Answer 1

The correct option is A $3.0$

$\overline{F}=q(\underset{V}{\to }\times \underset{B}{\to })$
$m\overline{a}=q(\overline{V}\times \overline{B})$
$\therefore \overline{a}.\overline{B}=0$
$(\hat{i}+7\hat{j}).(7\hat{i}-3\hat{j})=0$
$7x-21=0$
$x=3$