Question

An object of mass m = 2.9 g and charge Q = +42 µC is attached to a string and placed in a uniform electric field that is inclined at an angle of 30.0° with the horizontal. The object is in static equilibrium when the string is horizontal.
a) Find the magnitude of the electric field. b) Find the tension in the string. i know A is -mg + sin 30 * qE =0 but i don't know how to solve for it

Answer 1

(a) 
F= qE 

F sin 30.0° = mg 
= 0.0026(10) 
= 0.026 N 
F = 0.052 N 

E = F/q = 0.052 / 60µ = 867 N/C 

(b) 
T = F cos 30.0° 
= 0.0450 N