A plate of area 2 m2 is made to move horizontally with a speed of 2 ms-1 by applying a horizontal tangential force over the free surface of a liquid. The depth of the liquid is 1 m and the liquid in contact with the bed is stationary. Coefficient of viscosity of liquid = 0.01 poise. The tangential force needed to move the plate is α x 10-3 N. The valve of α is________.