A solid uniform disk of mass 19.0 kg and radius 70.0 cm (.7 m) is at rest FLAT on a frictionless surface. A string is wrapped around the rim of the disk and a constant force of 35.0 N is applied to the string. The string does not slip on the rim. The string is being pulled. When the disk has moved a distance of 6 m, what is the speed of the center of mass? Relevant equations (I think...): I=1/2MR^2 FR=Iα α=a/R So far, I have: FR=Iα FR=1/2MR^2(a/R) F=1/2Ma a=2*F/M=3.33333 m/s^2 and then, v^2=2*a*6m, since initial velocity is 0. v=7.26 m/s But this is wrong, and I'm not sure why. Please help!