Answer:
The speed of the ball is 0.8 m/s.
(D) is correct option.
Step-by-step explanation:
Given that,
mass of ball = 3.0 kg
length = 50 cm
We need to calculate the speed of the ball
Using relation between the centripetal force and tension


Where, m = mass
T = tension
r = radius
Put the value into the formula


Hence, The speed of the ball is 0.8 m/s.