The MEAN emf induced could not have been 0.12V and this is my explanation as to why. The rate of change of flux on the data sheet is given by delta (change in) flux over change in time. This is not a derivative. Hence this gives the emf when the change in flux is considered constant. However, the flux change was not constant as it is a coil rotating; the flux varies with a cosine function as the coil was initially perpendicular to the field. The change in flux linkage was 6x10^-2 Wbturns iirc and the time that this flux changed to 0 in was 0.5s, this gives 0.12V which is as if a conductor was dragged through a field at CONSTANT VELOCITY. However, you can model the coil as two conductors moving in circular motion where their velocity perpendicular to the field varies over time. Since the emf varies sinusoidally over time from t=0 to t=0.5s then the average emf must be 0.12v/sqrt(2) it is the root mean squared which gives 0.08V