physics
posted by phil .
A +50 micro coulomb and 30 micro coulomb charge are placed 50cm apart.
a)what is the direction and magnitude of thee electric field at a point P, in between them, that is 10cm from the 30 micro coulomb charge?
b)if an electron is placed at rest P, what will its acceleration be initially?
c)at what points along the line joining them is the electric field zero?
d)at what points along the line joining them is the potential zero?

q1…………….<  x >….q2
E2 P E1
E = k•q/r^2
E1 = k•q1/r1^2 = 9•10^9•50•10^6/(0.4)^2 = 2,8•10^6 V/m,
E2 = k•q2/r2^2 = 9•10^9•30•10^6/(0.1)^2 = 2.7•10^7 V/m,
E =E2 – E1 = 2,42•10^7 V/m.
(b)
ma =eE,
a =eE/m = 1.6•10^19•2.42•10^7/9. 1•10^31 =4.26•10^18 m/s².
(c)
x distance from the 50 micro coulomb)
k•q1/x²= k•q2/(0.5 –x)²
5/x² =4/(0.5–x)²
Solve for x. 
(d)
k•q1/x = k•q2/(0.5 –x)
5/x =4/(0.5–x)
Solve for x