PROBLEM $2\mathrm{.}6$:

At an unloading station, a block weighing $G=500N$ is released from a smooth surface at an angle of $30$ with a horizontal surface. Surface area of the block is $A=1000c{m}^2.$ The surface is greased with a pellicle having a thickness of $0\mathrm{.}025cm$ in order to get the blocks sliding with a constant downward speed of $U=1\mathrm{.}8\frac{m}{s}.$ Find the dynamic viscosity of the oil $($Pellicle: Thin oil layer between the blocks and the surface$).$