Circular Motion, a swinging ball and tension in string

[Sdarcy]

http://www.mech.uq.edu.au/courses/mech2210/yat/q/swinging_ball.jpg

The mass of the ball is m, as given below in kg. It is released from rest. What is the tension in the string (in N) when the ball has fallen through 45o as shown.

m[kg] = 3.335

I've used the formulae:

v = sqrt[2gL(sin alpha - sin alpha0)]
T = m(3 sin alpha - 2 sin alpha0)

and assumed that alpha0 = 0 degrees

I don't get the answer that the system is looking for (and it doesn't tell me what the right answer IS)

Any ideas where I've gone wrong?

Cheers...

 

[Doc Al]

v = sqrt[2gL(sin alpha - sin alpha0)]
T = m(3 sin alpha - 2 sin alpha0)

Where do these formulas come from?

Unless you've derived them yourself, stick to basic principles: Conservation of energy and Newton's laws.