This study investigates the physical mechanisms behind added mass and added damping during the transverse oscillation of a two-dimensional (2D) plate in a quiescent fluid. Added mass and added damping are defined as the components of the force in-phase and out-of-phase with the solid's acceleration, respectively. To achieve this goal, the force between the fluid and the solid is decomposed into physically meaningful components, establishing a direct link between the phenomena responsible for force generation and the added parameters. The study reveals that the added damping is solely dependent on vortex-induced and viscous forces, while added mass is predominantly influenced by inertia but also exhibits a significant contribution from vortex-induced and viscous forces. The results show that dimensionless frequency (⁠ β⁠) significantly influences added mass and added damping at low frequencies, with its impact decreasing as frequency increases. Additionally, added damping increases as the plate thickness ratio decreases, primarily due to the enhancement of the vortex-induced force mechanism. Reducing the thickness ratio (Δ) from Δ = 0.04 to Δ = 0.01 results in an increase in the damping coefficient by up to 60% within the intermediate range of the Keulegan–Carpenter (⁠KC⁠) number studied.