Question:
A block weighing $10 \mathrm{~N}$ travels down a smooth curved track $A B$ joined to a rough horizontal surface (figure 8-E5). 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, how far will it move on the rough surface?
Solution:
Work done, $\mathrm{W}=\mathrm{mgh}=10 \times 1$
$W=10 \mathrm{~J}$
Frictional force, $\mathrm{F}=\mu \mathrm{R}=\mu \mathrm{mg}=0.2 \times 10$
$F=2 N$
and $W=F s$
$\mathrm{s}=\frac{W}{F}=\frac{10}{2}=5 \mathrm{~m}$