You swing a rock in a circle at a constant speed perpendicular to the ground (up and down). The speed is 3m/s, the radius is 0.75m, the mass is 0.2 kg.
Draw free body diagrams at the top and the bottom.
What is the rope's tension at the top? What about the bottom?
As the speed decreases the tension decreases, what happens at top if the tension goes to zero?