A spool(initially at rest) is pulled on a smooth horizontal surface by constant horizontal force F, such that the spool comes into a state of sustained rolling motion. Kinetic energy of the spoool, after centre of mass of the spool has moved a distance d, is
1. Fd
2. Fdr1/r2
3. Fd(r1+r2)/r2
4. Fdr1/(r1+r2)
