Answer:
<em>1.187 x 10^8 m/s</em>
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Explanation:
the potential of the electric field V = 40 kV = 40000 V
the charge on an electron e = 1.6 x 10^-19 C
The energy of an accelerated electron in an electric field is given as
E = eV
E = 1.6 x 10^-19 x 40000 = 6.4 x 10^-15 J
This energy is equal to the kinetic energy with which the electron moves, according to the conservation of energy.
The kinetic energy =
where
m is the mass of the electron = 9.109 x 10^-31
v is the speed of the electron.
Equating the energy, we have
6.4 x 10^-15 =
6.4 x 10^-15 = 4.55 x 10^-31
= 1.41 x 10^16
= <em>1.187 x 10^8 m/s</em>