# A disc can roll without slipping , with out applying any external force on a 1) rough inclined plane 2) smooth inclined plane 3) rough horizontal surface 4) smooth horizontal surface

$a)\; 1,2\; and\; 3 \\ b) 1,3\; and\; 4 \\ c) 2,3\; and\; 4 \\ d)\; 1,2\; and\; 4$

On a smooth horizontal surface a body can roll if $V_{cm}=Rw$ is satisfied.
It can also roll on a rough horizontal surface if above condition is satisfied.
On a rough inclined plane , friction produces a torque.
edited Jun 22, 2014