Ball suspended by string with horizontal force equal to its weight

[robgazza]

Homework Statement

a ball of mass m is attached to a light string of length L and suspended vertically. A constant force, which magnitude F equals the weight of the ball, is applied horizontally to the ball. Determine the speed of the ball as t reaches the 90degree level in terms of L and g= 10 m/s^2

Homework Equations

not sure really!

http://img132.imageshack.us/img132/7374/phyiscsek4.jpg

The Attempt at a Solution

I honestly do not have a clue where to start on this question. Can anyone give me a start?

 

[robgazza]

desperately need help! :(

 

[berkeman]

Write the equations of motion for the ball. The string constrains how it moves, and the two forces acting on it are gravity downward and the horizontal pushing force. What are the kinematic motion equations that you should start with? Use x and y coordinates to separate the two components of position, velocity and acceleration...