Calculating Potential Difference in a Suspended Parallel Plate Capacitor

[kkevinzhang]

Homework Statement

A small object with a mass of 420 mg carries a charge of 30.0 nC and is suspended by a thread between the vertical plates of a parallel-plate capacitor. The plates are separated by 2.00 cm. If the thread makes an angle of 18.0° with the vertical, what is the potential difference between the plates?

Mass: 420 mg
Charge: 30.0 nC
Distance between plates: 2.00 cm
Thread of object: 18.0 degrees from vertical

Homework Equations

PE = -q(Vb-Va)
V = kq/r

The Attempt at a Solution

I just don't understand how the mass in the middle and the angle affects the problem.

 

[tiny-tim]

welcome to pf!

hi kkevinzhang! welcome to pf!

I just don't understand how the mass in the middle and the angle affects the problem.

draw a https://www.physicsforums.com/library.php?do=view_item&itemid=100" to find the horizontal force on the mass …

then calculate the potential difference which would produce that force

 

[kkevinzhang]

thanks!