When a body's weight is greater than the Buoyant force, the body sinks with an acceleration equal to ___
W−Fbm
The body has mass m and will sink with some acceleration, say a.
From the free body diagram, we see that the net force is equal to W−Fb
From Newton's second law, we can infer that the net force is equal to mass times acceleration
W−Fb=m×a
Or, a=W−Fbm