Hi. Can anyone explain to me what spin-up effects are? The context is a waterwheel that consists of an ordinary wheel with papercups with holes in the bottom suspended along the rim. It is stated that for this wheel there are two sources of damping: ordinary frictional damping and "inertial" damping which is caused by a spin-up effect. This is due to the fact that water enters the wheel at zero angular velocity but is thrown out at non-zero angular velocity through the holes in the bottom of the cups. How does this produce inertial damping?