A particle is released one by one from the top of two inclined rough surfaces of height $h$ each. The angles of inclination of the two planes are $30°$ and $60°$, respectively. All other factors (e.g., coefficient of friction, mass of block, etc.) are same in both the cases. Let $K_1$ and $K_2$ be the kinetic energies of the particle at the bottom of the plane in the two cases. Then

The system shown in figure is released from rest with mass $2 \mathrm{kg}$ in contact with the ground. Pulley and spring are massless, and function is absent everywhere. The speed of $5 \mathrm{kg}$ block when $2 \mathrm{kg}$ block leaves the contact with the ground is (force constant of the spring $k:=40 {\mathrm{Nm}}^{-1}$and $g=10 {\mathrm{ms}}^{-2}$)

A large slab of mass $5 \mathrm{kg}$ lies on a smooth horizontal surface, with a block of mass $4 \mathrm{kg}$ lying on the top of it. The coefficient of friction between the block and the slab is $0.25.$ If the block is pulled horizontally by a force of $F=6 \mathrm{N},$ the work done by the force of friction on the slab, between the instants $t=2 \mathrm{s}$ and $t=3 \mathrm{s}$, is $\left(g=10 \mathrm{m} {\mathrm{s}}^{-2}\right)$