Calculate the magnitude of the force acting on the -8 uC due o the other charges

Question

Physics : Electrostatics 

Charges of +2, +3 and -8 uC are placed in air at the vertices of an equilateral triangle of side 10cm. Calculate the magnitude of the force acting on the -8 uC due o the other charges

Answer 1

Student,

 

This entails a tedious calculation.  You have 2 pairs of charges (the +2 with the -8 μC, and the +3 with the -8 μC) to work with.  Use Coulomb's law to get the magnitude of the electric force for each pair (being careful with the units).

 

F_ij = [1/(4πε)] q_iq_j/r_ij²

 

Then use trigonometry to project each magnitude along the x and y axes to get the x and y components of each force.  Be careful with how you choose the signs of the components, because the force due to each positive charge must point from the -8 μC charge toward the positive charge.  Once you have the components F_1x, F_1y, F_2x, and F_2y of the 2 forces, the magnitude of the net force will be

 

F = √[(F_1x + F_2x)² + (F_1y + F_2y)²]