What am I doing wrong in this problem?

Question

The County Fair Swing carries the mass of riders and chairs in a circular path in a horizontal plane while suspended by cables or chains. Let's assume that:

Each chair with riders is supported by a single cable

The tension in the cable equals 2 x the total weight riders and chair

The speed of the center of mass at the end of the cable is 10 m/s.

Determine the radius of the circular path in meters.


Selected Answer:
50

 

T=mv^2/r so r=10^2/2

100/2=50

50=r

Answer 1

"The tension in the cable equals 2 x the total weight riders and chair ..."  means

 

 T=2mg

And, as you mentioned  T=mv^2/r

 

So,    2g=v^2/r

 

That is   r=v^2/2g=100/(2*9.8)=5.1 (m)