The dynamics of an isolated straight stripe domain is investigated in three samples with various damping constants. If an in-plane field is not present, the dynamic behavior of the stripe domain agrees well quantitatively with the horizontal Bloch line theory independent of the damping constant. If the in-plane field

is applied parallel to the walls, however, the experimental results gradually deviate from the theory as the damping constant becomes smaller or the in-plane field becomes larger. For example, the peak velocity is independent of

and the critical field for velocity breakdown decreases with increasing

for a film with very low damping.