Why Is Tension 3mg at the Lowest Point?

[duplaimp]

Homework Statement

An object with mass m is attached to a fixed structure with a rope with dimension R like in the figure. The object is dropped. Why is the tension in the lowest point of the movement 3mg?

 

[Chestermiller]

Using conservation of energy, what is the velocity of the mass at the lowest point? What is the radial acceleration at the lowest point? Treating the mass as a free body, what is the radial component of the force balance at the lowest point?