Calculating the Radius of a Circle for Masses Attached by a Cord

[ScienceGeek24]

Homework Statement

A block of mass m1=2kg is attached to a cord. The cord goes down through a hole in the table and is attached to mass m2=4 kg hanging below the table. The 2 kg mass moves on the table in a circle at a speed of 3.5 m/s the table top is friction less and there is no friction between the cord and the side of the hole. What is the radius of the circle if the 4 kg mass remains at rest?

Homework Equations

Sum of force x direction m1: T=mv^2/r

Sum of forces y direction m1: N-mg=mv^2/r

Sum of forces x direction m2: Mg-t= Mv^2/r

The Attempt at a Solution

I have tried to use this equations and i cannot come up wit the solution. Do i have my equation correctly in this problem?

 

[thephysicsm]

I guess you use orbital length to get the answer :P