The slope of a force versus mass graph has units of N/kg, which can also be expressed as m/s². This is derived from the relationship where slope equals rise over run, with rise being the change in force and run the change in mass. In the SI system, force is measured in Newtons and mass in kilograms, leading to the conclusion that the slope represents acceleration. The formula F = m*a supports this, as dividing force by mass yields acceleration. Understanding this relationship clarifies the units of the slope and its significance in physics.