A particle with negative charge $q$ and mass $m = 2.58 \times$ $10 ^ { - 15 } \mathrm { kg }$ is traveling through a region containing a uniform magnetic
field $\vec { \boldsymbol { B } } = - ( 0.120 \mathrm { T } ) \hat { \boldsymbol { k } }$ . At a particular instant of time the velocity
of the particle is $\vec { \boldsymbol { v } } = \left( 1.05 \times 10 ^ { 6 } \mathrm { m } / \mathrm { s } \right) ( - 3 \hat { \imath } + 4 \hat { \jmath } + 12 \hat { \boldsymbol { k } } )$ and
the force $\vec { \boldsymbol { F } }$ on the particle has a magnitude of 2.45$\mathrm { N }$ . (a) Determine the charge $q .$ (b) Determine the acceleration $\vec { a }$ of the particle.
(c) Explain why the path of the particle is a helix, and determine
the radius of curvature $R$ of the circular component of the helical
path. (d) Determine the cyclotron frequency of the particle. (c) Explain why the path of the particle is a helix, and determine
the radius of curvature $R$ of the circular component of the helical
path. (d) Determine the cyclotron frequency of the particle.
(e) Although helical motion is not periodic in the full sense of the
word, the $x$ - and $y$ -coordinates do vary in a periodic way. If the coordinates of the particle at $t = 0$ are $( x , y , z ) = ( R , 0,0 ) ,$
determine its coordinates at a time $t = 2 T ,$ where $T$ is the period
of the motion in the $x y$ -plane.