Help needed on finding speed for circular motion

Question

A radio controlled ariplane is suspended from a 0.80 m string. The plane revolves in a circle at a constant speed. The angle the string makes from the vertical is 60º. What is the speed of the plane?

 

I just know that centripetal force F_C = Tsin60 and the radius r=.80(sin60)

Answer 1

A radio controlled ariplane is suspended from a 0.80 m string. The plane revolves in a circle at a constant speed. The angle the string makes from the vertical is 60º. What is the speed of the plane?
 
I just know that centripetal force FC = Tsin60 and the radius r=.80(sin60)

 

Solution:

You do not need the centripetal force in this problem

All you need is R and because  tan θ = V²/gR

 

R= 0.8sin60=0.693 m, then tan 60 = V²/ 9.81 m/s² x 0.693 m

 

V² = 9.81 m/s2 x 0.693 m x tan 60 = 11.77 m²/s², V = 3.43 m/s