When the electron enter into the electric field, the electric force acts on it. In this case the electric force is calculated using the following expression:

Fe = -e*E

Where -e is the charge of the electron and E is the electric field strength.

Applying Newton's second law, we can calculate the acceleration experienced by the electron:

F = m*a

In our case, F is the electric force and m is the mass of the electron, i.e.:

Fe = me*a

a = Fe/me = (-e*E)/me

a = (-1.602*10^-19)(8.0*10^3)/(9.109*10^-31)

a = -1.4*10^15 m/s^2

As the charge of the electron is negative, the direction of the force is contrary to the field, that is, along the -y axis.

To find the time that it takes to stop, we apply the equation of acceleration:

a = (v – v0)/t

Where v0 is the initial speed and v is the final velocity, which in this case is zero.

t = (v – v0)/a = (0 – 2.0*10^-6)/(- 1.4*10^15)

t = 1.43*10^-21 s

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