The deceleration experienced by a moving motorboat after its engine is cut off, is given by dv/dt = – kv3 where k is constant. If v0 is the magnitude of the velocity at cut-off, the magnitude of the velocity at a time t after the cut-off is
(a) v0/√(2v02kt + 1)
(b) v0e-kt
(c) v0/2
(d) v0
