A computationally efficient five-degree-of-freedom dynamic model was developed to simulate the motion of a magnetic head slider under the conditions of moving-bump collision and of contact due to an expanding protrusion on the slider for thermal flying-height control, with consideration of intermolecular forces. Compared to results obtained without intermolecular forces for a bump on the rotating disk, the intermolecular forces cause a significantly greater normal contact force, a larger roll angle and a larger off-track displacement under nonzero skew. When an expanding protrusion on the slider reaches a position close to the disk surface, the intermolecular forces pull the slider into contact at an earlier time and keep the protrusion in contact for a longer duration, which, with friction under nonzero skew, results in a substantially greater off-track displacement.