Here, forced vibration of a rectangular plate with a side crack of arbitrary length, orientation and position is studied by the Ritz method. Simply supported and clamped boundary conditions are used in the analysis. Numerical results obtained from the Ritz method are validated by finite element method software (ABAQUS). Good matching was found for first five modes. Mobility curves are presented for variation in force location, crack length, crack orientation and crack position in a square plate. Normalized mobility is found to increase with an increase in crack length ratios and decrease with an increase in crack angle. Again, it is observed that a change in crack position from side towards middle increases the normalized mobility. The results can be used for mobility-based crack detection.