Two floating pens

The layout of the Leonov is a little hard to figure watching the film but the part that rotates is apparently the crew quarters with bunks and common area and, the the medical bay. The control room and technical areas are in the central, non-rotating portion. I figure Hyams, an annoying director who presided over stupid SF films like Outland and Capricorn One, didn't want to be accused of imitating Kubrick (small chance) by including shots intended to show this. So in 2001 we see the stewardess wearing velcro booties and walking carefully in them and we see the Discovery astronauts transitioning from the ships central corridor to the ladder down to the centrifuge... But nothing like this is shown in 2010. No attempt is made to show free fall aboard the Leonov until the floating pens.

I remember seeing this back in 1984 and there was a low murmur throughout the audience when this happened. It was a wow moment.

Not all of the Leonov rotated, and most likely the pen scene happened in a non-rotating part. If you remember, the scene also shows them looking out of the window, and the view isn't shifting with any rotation. So I'd say zero-g in this scene, 100%.