Determine the initial acceleration of the 15-kg block

[javii]

Homework Statement

Determine the initial acceleration of the 15-kg block if (a) T = 23 N and (b) T = 26N. The system is initially at rest with no slack in the cable, and the mass and friction of the pulleys are negligible.
I have attached a picture of the problem.

The Attempt at a Solution

a)
I know, that there is a normal force, that I need to find.
I do that by setting the sum of forces in y-direction = 0
0=m*T*cos(30)+N
then I get N=0 ?
I don't think that is correct.
B)
I don't know how to solve this part either.

 

[PetSounds]

What's the definition of normal force?

 

[TomHart]

Where did you come up with mTcos30. That doesn't make sense to me. It doesn't make sense that you are multiplying mass times the tension and it doesn't make sense why you are using cos30. And you forgot one of the forces in y direction - the weight. But starting with summing forces in y direction is good. And then do x direction.

Edit: By the way, what is "G"?