Monobot, the single servo robot

How many motors do you need to make a robot which can move in 2 dimensions? Most need 2, either left-right differential like a tank, or one for going forward and one for steering, like cars. There are experiments to achieve steerable robots using just one actuator, notable ones are the 1STAR from UC Berkeley (which has 6 legs, the middle legs are elastic) and the Monospinner from ETH Zurich (which can even fly), but they require complex and delicate mechanisms and control systems.

Introducing Monobot, the single servo robot. This robot has only 2 parts, the base and the foot, which are connected by a servo motor. But how could this robot move?

The key is center of mass, friction, and acceleration. The mass of the robot is located on the upper part ('the body') and is offset to the front, near the batteries. When the motor is accelerating to one direction, normal force (N) on one side of the foot is greater than the other, and since static friction limit (fsmax) is proportional to