An electron is fired directly toward the center of a large metal plate that has
ID: 1530203 • Letter: A
Question
An electron is fired directly toward the center of a large metal plate that has excess negative charge with surface charge density 9.00×10-6 C/ m2. If the initial kinetic energy of the electron is 150 eV and if the electron is to stop (owing to electronstatic repulsion from the plate) just as it reaches the plate, how far from the plate must it be fired?
(8c23p39) An electron is fired directly toward the center of a large metal plate that has excess negative charge with surface charge density 9.00x10-6 C/ m2. If the initial kinetic energy of the electron is 150 ev and if the electron is to stop (owing to electronstatic repulsion from the plate) just as it reaches the plate, how far from the plate must it be fired? Submit Answer Tries 0/8 What is the magnitude of the acceleration? Submit Answer Tries 0/8Explanation / Answer
Given
surface charge density is sigma = 9*10^-6 C/m2
so the for a metal plate electric field is E = sigma / 2*epsilon not
F/q = sigma / 2*epsilon not
ma/q = sigma / 2*epsilon not
a = sigma*q / m*2*epsilon not
= (9*10^-6*1.6*10^-19)/(9.11*10^-31*2*8.854*10^-12) m/s2
= 8.926364190204*10^16 m/s2
kinetic energy of the electron is k.e = 0.5 mU^2 = 150 eV = 150*1.6*10^-19 J = 2.4*10^-17 J
velocity of he electron is U = sqrt(2*k.e/m)
U = sqrt(2*2.4*10^-17/9.11*10^-31) m/s
U = 7258743.1666951757 m/s
using equations of motion
v^2 - u^2 = 2as
as the electron momentarily stops when it reaches nearer to the place because of electrostatoic repulsion force
soe v= 0 ==> s = u^2/2a = 7258743.1666951757^2/(2*8.926364190204*10^16) m
= 0.0002951333333 m
=0.295133 mm
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