Work-Kinetic Energy Theorem- Pendulum on a String

[hks118]

Homework Statement

A ball of mass m=7kg attached to a massless string of length R=3 is released from the horizontal . Assume g=10m/s² throughout the problem.

a. Using thee Work-Kinetic Energy Theorem, find the magnitude of the velocity of the ball when it is at its lowest point (IE the string is vertical).

b. Find the tension of the string at that point.

Homework Equations

Work-Kinetic Energy Theorem: Work_net=KE_f-KE_i
KE= 1/2 m v²

The Attempt at a Solution

I'm not exactly ure how to begin. I think that KE_i=0 but that's about it.

 

[rl.bhat]

When the ball reaches the lowest point, it falls through a height R. What is the fall in PE?
Using conservation of energy find KE at the lowest point and hence the velocity.