During that scene, Stone's leg gets wrapped up in some parachute cabling. She then starts slowly rotating around whatever the cabling is stuck on. Then she grabs the strap attached to Kowalski. She's still rotating. In order to hold onto him, she's providing a centripetal force. After releasing him, she finally rotates into another part of the station, and works her way to the airlock.
I look forward to being able to provide some evidence of this once the film is released on blu-ray.
We have 4 things of import in this image.
- Stone's ongoing motion, which are the lines behind her in my crude drawing.
- A, the force that Stone is exerting on Kowalski.
- B, the force Kowalski is exerting on Stone. This is equal and opposite to A.Newton's 3rd Law If it wasn't equal and opposite, then Kowalski would be moving toward or away from Stone at this moment.
- C, the centripedal force exerted on Stone by the parachute cabling wrapped around her foot. This force is going to be equal to A + the amount of force needed to keep Stone alone moving in the arc.
C is larger here due to it needing to pull the mass of both Kowalski and Stone. Once Kowalski is released, then C just needs to pull Stone, which drastically reduces C's magnitude.
In the scene, while C is large, Stone's leg is slipping out of the parachute cabling. Once C is reduced, this stops, and she soon swings into the hull of the ISS.