what is the use of the rotating drum in the kymograph?

Question

kymograph

Answer 1

It provides the time axis for the measurement being graphed by the moving pen or other marker. The drum rotates at a given smooth rate and the paper is marked with time units, either pre printed or by twitching the measuring pen and the pen shows air or blood or other pressure by moving across the paper perpendicular to the rotation.

Answer 2

to create momentum