Three charges are arranged in a line. From left to right, the charges are:

Question

Q1= -8mC, Q2 = +3mC and Q3 = -4mC. The distance between Q1 and Q2 is 0.3 m, and the distance between Q2 and Q3 is 0.2 m. Calculate the net electrostatic force on Q3.

Answer 1

Add the forces due to Q1 and Q2, upon Q3. They will be in opposite directions. Use Coulomb's law.

Note that the distance of Q1 from Q3 is 0.5 m

It will be a useful learning exercise, more so than having someone do it for you.

Answer 2

Yes

Answer 3

-1.5 N