Finding charge magnitude from tension and kinetic energy with electric force

[CombatVetUSMC]

Homework Statement

An electrically neutral model airplane is flying in a horizontal circle on a 2.5-m guideline, which is nearly parallel to the ground. The line breaks when the kinetic energy of the plane is 50 J. Reconsider the same situation, except that now there is a point charge of +q on the plane and a point charge of -q at the other end of the guideline. In this case, the line breaks when the kinetic energy of the plane is 51.5 J. Find the magnitude of the charges.

Homework Equations

T$_{}max$ = 2*KE$_{}1$/r
F= F$_{}c2$ - T$_{}max$
q=√Fr$^{}2$/k

The Attempt at a Solution

T$_{}max$= 2(50J)/2.5m= 40J/m

not sure how to get F$_{}c2$

 

[tiny-tim]

Welcome to PF!

Hi CombatVetUSMC! Welcome to PF!

T$_{}max$ = 2*KE$_{}1$/r
F= F$_{}c2$ - T$_{}max$
q=√Fr$^{}2$/k

What about KE₂ ?

50/r = KE₁/r = T

51.5/r = KE₂/r = T + F_q ​