A proton is fired from origin with velocity `vecv=v_0hatj+v_0hatk` in a uniform magnetic field `vecB=B_0hatj`.

Options

A. its z-coordinate can never be negative
B. its x-coordinate can never be negative
C. its x-and z-coordinates cannot be zero at the same time
D. its y-coordinate will be proportional to its time of flight

Answer

(b,d)

Explanation

The path of the particle will be helix as shown in fig. Clearly
x-coordinate is always negative. z-coordinate can be negative
and positive both. X and z coordinate will be zero at the same
time at points A, C etc
`y=v_0t implies ypropt`