The centripetal force is the force that keeps an object in a circular motion.
Centripetal force= mω²r
Where m is the mass, ω is angular velocity and r is the length of the string.
But ω = v/r. Where v is the tangential speed.
∴ F = mω²r = mv²/r
F = (1.5 × 6²) / 0.5
= 108 N
Mass of object,
Length of string,
Now, centripetal force F of a object moving in given radius r and mass m moving with velocity v.
Here , object moves along the ends of string. Therefore, radius is equal to length of string.
Putting values of m,v and r in above equation.
Hence, this is the required solution.