Q. Relationship between number of hours worked and unemployment?
In all models we presume a negative relationship between number of hours worked and unemployment. If number of hours worked increases, unemployment will fall and vice versa. This assumption would be true if the workforce is constant and individuals in labor force either work full time or not at all.
In reality, this relationship need not hold. We may see an increase in labor force (for instance from immigration) which is larger than the increase in employment which would lead to an increase in both hours worked and unemployment however we disregard this possibility.