Answer
$R=3.16\times 10^{-4} m$
Work Step by Step
As the magnetic force produces the centripetal force so these two forces are equal in magnitude. This can be written as:
$qvB=\frac{mv^2}{R}$
Rearranging the formula to solve for $R$:
$R=\frac{mv^2}{qvB}$
$R=\frac{mv}{qB}$
We then plug in the known values to obtain:
$R=\frac{9.109\times 10^{-31}(1.11\times 10^7)}{1.6\times 10^{-19}(0.2)}$
$R=3.16\times 10^{-4} m$
