Finding the tension in the thread

[JKhim]

Homework Statement

A tiny, 0.60g ball carries a charge of magnitude 8.0 mircoC. It is suspended by a vertical thread in a downard 300 N/C electric field. What is the tension in the thread if the charge on the ball is (a) positive, (b) negative?

Homework Equations

E=F/q or E=mg/q

When i use that formula something is missing because I've tried to match the final answer from the other thread with the same exact problem he wants to solve too

 

[Miles123K]

Try finding the electric force on the ball caused by the field.

 

[JKhim]

Still finding the final formula for this problem

 

[JKhim]

This are the answers
(a) 8.3 mN; (b) 3.5 mN.

 

[TheMercury79]

All the forces are vertical. In both cases you have an electric force and gravitational force, in one case they are opposite.
In what directions does a positive vs. negative charge move in the electric field? Does a positive charge go against or
along the field lines?

 

[haruspex]

When i use that formula something is missing

it will save a lot of time and guesswork if you post your own working and answer in the first place.

 

[Orodruin]

This are the answers
(a) 8.3 mN; (b) 3.5 mN.

Are these your answers or the book’s answer? If yours, how did you arrive at them? If the book’s, note that forum rules requires you to show effort.

 

[Delta2]

Start by enumerating all the forces that are acting on the ball. There are three different forces... Which are these forces and which is their direction and magnitude? Once you answer this question use that $\sum \vec{F_i}=0$ that is that the sum of all forces must equal zero since the ball is at equilibrium.