Help with physics problem from image

[UrbanXrisis]

http://home.earthlink.net/~urban-xrisis/phyyy002.jpg

I'm really not sure what to do here. ANY hints would be helpful.

 

[Doc Al]

You'll need to use conservation of energy and Newton's 2nd law (consider centripetal acceleration). Hint for part b: At the top of the motion there is a minimum speed to maintain a taut string.

 

[UrbanXrisis]

the formula PE=KE?

so the PE when the ball is below the peg has to equal the KE after it hits the peg?