Question

Solve this problem and show the complete solution.

Three point charges are located along x-axis.

Given q1 = + 3.5 x 10-6 C

q2 = + 8.5 x 10-6

C

q3 = - 5.0 x 10-6 C

r1 on 2 = 2.0m

r3 on 2 = 1.0m

k = 9 x 109 N.m2/C2

a) Find F 1 on 2 and direction.

b) Find F 3 on 2 and direction.

c) Find the RF acting on q2 and direction.

Enrichment

Answer 1

a) Find F 1 on 2 and direction using Coulomb's law:

$$F_{12}=k\frac{q_1q_2}{r_{12}^2}=0.0668\text{ N}.$$

The force caused by 1 on 2 acts to move 2 away from 1.

b) Find F 3 on 2 and direction:

$$F_{32}=k\frac{q_3q_2}{r_{12}^2}=-0.382\text{ N}.$$

Since these charges are of opposite signs, 3 acts on 2 to attract 2 toward 3.

c) The resulting force is

$$R_R=F_{12}+F_{32}=-0.315\text{ N},$$

which means that 2 will be pushed by 1 and pulled by 3 toward 3.