
A force versus distance curve (Naval Research Laboratory, Washington, DC) 
In an FFM experiment, it is quite easy to compute the amount of dissipated energy. The energy which is needed to move the tip over a distance ds is given as dW=F ds where F is the Friction force. The amount of dissipated energy is hence given by the area of the friction hysteresis during one friction loop.
It is easy to understand, that the amount of didssipated energy is highly dependent on the applied normal force. This can be seen in the Figure.
