As the velocity is constant, the result of the forces in the sled is zero. If \(T_x\) is the horizontal component of the traction and \(F_{at}\) is the frictional force:
\(F_R=0\iff T_x=F_{at}\iff T\cos30^o=\mu N\iff \\\\ T\cos30^o=\mu P\iff 200\cdot\dfrac{\sqrt3}{2}=\mu (500\cdot10)\iff 100\sqrt3=5000\mu\\\\\mu=\dfrac{100\sqrt3}{5000}\iff \mu=\dfrac{\sqrt3}{50}\Longrightarrow\boxed{\mu\approx0,035}\)
