The work done by all the forces (external and internal) on a system equals the change in

A force $F$ acting on an object varies with distance $x$ as shown here. The force is in $\mathrm{N}$ and $x$ is in $\mathrm{m}.$ The work done by the force in moving the object from $x=0$ to $x=6 \mathrm{m}$ is

A block weighing $10 \mathrm{N}$ travles down a smooth curved track $AB$ joined to a rough horizontal surface (figure). The rough surface has a friction coefficient of $0.20$ with the block. If the block starts slipping on the track from a. point $1.0 \mathrm{m}$ above the horizontal surface, the distance it will move on the rough surface is: