a ball of mass M is attached to a string of length L and moves in a circle in a vertical plane. at the top of the circular path, the tension in the string is twice the weight of the ball. at the bottom, the ball just clears the ground. there is no air resistance.
in terms of M, L, and g, find:
(a) the magnitude and direction of the net force on the ball at the top
( the speed v of the ball at the top

if the string is cut when the ball is at the top, find (in terms of M, L, and g):
© the time it takes the ball to reach the ground
(d) the horizontal distance the ball travels before hitting the ground

i have no idea how to solve this... please help me out

A good way to approach systems like this is to draw a picture. First, since the ball is released at the top of the swing, the picture should probably be drawn with the ball at the top of the string.

The next point is that you'll have to make use of the dimensions of the problem to determine the height of the ball off the ground (this part's pretty easy).

Then you should go through and determine the speed at which the ball is moving. To do this, you'll have to make use of the fact that the ball is accelerating. First, count up all of the forces on the ball (don't forget any of 'em!), then use Newton's second law (F=ma) to determine the acceleration. Since you should be aware of the relationship between the acceleration and speed of an object in circular motion, that should give you the speed of the ball.

This, then, provides you with the initial conditions to the next stage of the problem, when the string is cut. When that happens, you should know the velocity of the ball, as well as all forces acting upon it. This should give you its trajectory, which should tell you when and where it will hit the ground.

Does that help?