Question

To practice Problem-Solving Strategy 21.1 Coulomb's Law.

Three charged particles are placed at each of three corners of an equilateral triangle whose sides are of length 3.7 cmcm . Two of the particles have a negative charge: q1q1 = -6.9 nCnC and q2q2 = -13.8 nCnC . The remaining particle has a positive charge, q3q3 = 8.0 nCnC . What is the net electric force acting on particle 3 due to particle 1 and particle 2?

Part B

Find the net force ΣF⃗3ΣF→3 acting on particle 3 due to the presence of the other two particles. Report you answer as a magnitude ΣF3ΣF3 and a direction θθ x axis.

Answer 1

Let us assume ABC is the given equilateral triangle with side AC as its base and the positive charge is at the point A. If charges and are at points B and C respectively, then the attractive Coloumbian electric forces between q3 & q1 and q2 & q3 will be along and with .

So, according to Coloumb's Law of electrostatic force,

required electric force acting on particle 3 due to particle 1,

and , required electric force acting on particle 3 due to particle 2,

[ where,

and , ]

The magnitude of the required net electrical force acting on charge q3 at point A is given by,

,

where, triangle ABC being a equilateral triangle, ,i.e., angle between and ;

and   & .

So,   

with an angle of direction = 40 degrees with the base AC of the triangle ABC

[by the formula, ]