Hi all, this is not a homework question so it does not have a given answer and the question may be vague. It is something I need to know for my project, hope you guys can just give a few tips to point me in the right direction. Thanks. 1. The problem statement, all variables and given/known data A cylinder of radius r metres, length L and mass m kg is immersed d metres in the sea. It is at static equilibrium along the z-axis. Friction is not negligible. If there is an underwater current of velocity v metres/sec, what is the resultant velocity of the cylinder? When the cylinder is moving at velocity v_c, I could add the velocity vectors v and v_c to get the resultant velocity, but I also wish to factor in the mass of the cylinder. How should I do that? 2. Relevant equations none 3. The attempt at a solution When the current hits the cylinder, the cylinder accelerates and frictional force increases. The cylinder then reaches terminal velocity. But what I don't get is how to calculate the force of the current on the cylinder and the frictional force .