Friday, May 7, 2010

An electron with velocity v = 2.0x10-6 m/s directed along +y axis enters in a region of uniform electric field, E = 8.0 x 103 V/m directed along +y...

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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