The retardation experienced by a moving motor boat, after its engine is cut off, is given by 𝑑𝑢 𝑑𝑡 = −𝑘𝑣 3 , where 𝑘 is a constant. If 𝑣0 is the magnitude of the velocity at cut-off, the magnitude of the velocity at time 𝑡 after the cut-off is

Question : The retardation experienced by a moving motor boat, after its engine is cut off, is given by 𝑑𝑢 𝑑𝑡 = −𝑘𝑣 3 , where 𝑘 is a constant. If 𝑣0 is the magnitude of the velocity at cut-off, the magnitude of the velocity at time 𝑡 after the cut-off is