Think of a penny a distance x away from the center of a quot;lazy Susanquot;. My homework indicates that it's angular momentum is conserved when...

Think of a penny a distance x away from the center of a "lazy Susan". My homework indicates that it's angular momentum is conserved when you move the penny closer toward the center or father. My question is: why is angular momentum conserved at all? Isn't there a force of friction being applied between the penny and the platform of the lazy susan?