Question

Can you walk on a frictionless surface ? Why / Why not ?

Answer 1

No, we need friction to walk. By taking a step forward we apply a backwards force against the floor. The only reason that we don't slip is because friction counteracts that backwards force. (Newton's law: For every action there is an opposite, but equal, reaction). The only way to get across a frictionless floor would be to throw something (the opposing force propelling you backwards).