Hi there! :)
We can begin by doing a summation of forces on the ball. In the horizontal direction, we have the force of tension:
[tex]F_{Net} = T[/tex]
The tension force results in a centripetal force experienced by the ball. The equation of centripetal force is equivalent to:
[tex]F_C = m\omega^2 r[/tex]
[tex]F_C[/tex] = Centripetal force (N)
m = mass of ball (0.22 kg)
ω = angular speed of ball(? rad/sec, must convert rpm to rad/sec)
r = radius/length of string (1.0 m)
We must begin by converting rpm to rad/sec:
[tex]\frac{50 rev}{min} * \frac{2\pi rad}{1 rev}* \frac{1 min}{60 sec} = 5.236 \frac{rad}{s}[/tex]
Now, we can set tension equal to the centripetal force and solve. [tex]T = F_{Net} = F_C\\\\T = m\omega^2 r\\\\T = (0.22)(5.236^2)(1) = \boxed{6.031 N}[/tex]