Three particles are arranged on coordinate axes as shown above. Particle A has c

ID: 2152105 • Letter: T

Question

Three particles are arranged on coordinate axes as shown above. Particle A has charge qA = -0.20 nC ,

and is initially on the y-axis at y = 0.030 m. The other two particles each have charge qB = +0.30 nC and

are held fixed on the x-axis at x = -0.040 m and x = +0.040 m , respectively.

(a) Calculate the magnitude of the net electric force on particle A when it is at y = 0.030m, and state its direction.

(b) Calculate the magnitude and direction of the electric field at qA .

(d) Calculate the electric potential at point O.

(e) Calculate the electric potential energy of a charge qc = -0.20 nC brought from infinity to the point O.

(f) Particle A is then released from rest. Qualitatively describe its motion over a long time.

(a)

The horizontal components of the force cancel each other,

So the verical components remain.

So,F=(2kqQ/r2)*3/5 in the -y direction(downwards)

=(2*9*109*3*0.2*0.3*10-9*10-9)/5*0.05*0.05

=2.59*10-7 N in the -y direction(downwards)

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