A block of mass 1.5 kg kept on a rough horizontal surface is given a horizontal velocity of $10 \mathrm{~ms}^{-1}$. If the block comes to rest after travelling a distance of 12.5 m , the coefficient of kinetic friction between the surface and the block is (acceleration due to gravity $=10 \mathrm{~ms}^{-2}$ )

Three blocks of masses $2 \mathrm{~m}, 4 \mathrm{~m}$ and 6 m are placed as shown in figure. If $\sin 37^{\circ}=\frac{3}{5}, \sin 53^{\circ}=\frac{4}{5}$, the acceleration of the system is

Two masses $m_1$ and $m_2$ are connected by a light string passing over smooth pulley. When set free $m_1$ moves downwards by 3 m in 3 s . The ratio of $\frac{m_l}{m_2}$ is $\left(g=10 \mathrm{~ms}^{-2}\right)$