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The work done by the frictional force on a surface in drawing a circle of radius \( r \) on the surface by a
\( \mathrm{P} \) pencil of negligible mass with a normal pressing

W force \( \mathrm{N} \) (coefficient of friction \( \mu_{\mathrm{k}} \) ) is:
(1) 0
(2) \( -2 \pi r^{2} \mu_{k} \mathrm{~N} \)
(3) \( -3 \pi r^{2} \mu_{\mathrm{k}} \mathrm{N} \)
(4) \( -2 \pi \mathrm{r} \mu_{\mathrm{k}} \mathrm{N} \)
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