How to calculate the velocity of a object falling due to gravity through a pipe (vertical) where the fluid is flowing in upward direction? Please ignore the frictional force & just consider F net = F (gravity) - F (drag) - F (force the fluid exerting on the object during upward flow) - F(buoyancy) Note: Buoyancy force also can be ignored for simplicity. The drag is quadratic drag, not stokes'. Consider the terminal velocity. Please devise the general way to calculate this.