A particle of mass `1xx 10^(-26) kg` and charge `+1.6xx 10^(-19) C` travelling with a velocity `1.28xx 10^6 ms^-1` in the `+x` direction enters a region in which uniform electric field E and a uniform magnetic field of induction B are present such that `E_x = E_y = 0, E_z= -102.4 kV m^-1, and B_x = B_z =0, B_y = 8X 10^-2.` The particle enters this region at time `t=0.` Determine the location (x,y,z coordinates) of the particle at `t= 5xx10^-6 s.` If the electric field is switched off at this instant (with the magnetic field present), what will be the position of the particle at `t= 7.45xx10^-6 s` ?

Options

A. net force acts o the particle long the +ve z-direction.
B. net force acts on the particle alog -ve z-direction
C. net force acting on particle is zero
D. net force acts in xy-plane

Answer

C

Explanation

`F_e=qE=(1.6xx10^-19)(-102.4xx10^3)hatk`
`=(-1.6384xx10^-10hatk)N`
`F_m=q(vxxB)`
`=(1.6xx10^-19)[(1.28xx10^6hati)xx(8xx10^-2hatj)]`
`=(1.6384xx10^-14hatk)N`
Now we can see that
`F_e+F_m=0`