问答题 (清华大学2006--2007学年春季学期期中考试试题)A viscous liquid of constant density and viscosity falls due to gravity between two parallel plates a distance 2h apart，as in Fig．4-60．0ne plate is moving at speed w ₀ ．The flow is fully developed，that is，w=w(x) only．There are no pressure gradients，only gravity Set up and solve the Navier-Stokes equation for the velocity profile w(x)．