1. The problem statement, all variables and given/known data Does the delay of propagation of pressure gives a torque during a short time ? A disk full of a liquid turns at a constant angular velocity w around the red axis. At a time, a valve move out, this will increase quickly the pressure inside the liquid. 1/ Draw the lines of equal pressure from the valve 2/ Draw the forces from this additionnal pressure 3/ Is there an additionnal torque ? 2. Relevant equations Speed of sound in the fluid 3. The attempt at a solution 1/ & 2/ 3/ Yes, the torque from F1 is greater than F2 Is it correct ?