In Duchamp's picture you have both: the sensation of the movement in the time sequence and the very existence of the movement in the subject 'nude'.
Before it was common to freeze a nude, lying or standing, in the picture. To descend a nude was new! Duchamp confirmed it by writing the title in the lower left corner.
A painting, he said, 'is the diagram of an idea'.
‘Nu descendant un escalier, n°2’ - 147 cm × 89 cm (58” × 35”)
Collection Philadelphia Museum Of Art