Answer: a) 42 *10^-3 m= 42 mm; b) 10.40 *10^-6 s=10.40 μs
Explanation: In order to response this problem we have to consider the Newton law for the circular movement,
Fm=m*ac where Fm is the magnetci force and ac the centripetal acceleration which is equal to v^2*R ( the raduis of teh curcular trajectory)
Fm=e*v*B considering that v and B are perpendicular
then we have:
e*v*B=m*v^2/R so
R=m*v/(e*B)= 9.1*10^-31*1.44*10^7/(1.6*10^-19*1.95*10^-3)= 42 mm
Then to calculate the time to complete one revolution ( period)
we know that ω=v*R and T= 2π/ω
then we have:
ω=1.44*10^7*42*10^-3=604.8 *10^3 rad/s
T=2*π/604.8 *10^3 = 10.4 μs