# Problem 7-62 Energy cons. with friction - Part 2 - C

A pen of mass $0.057 \;kg$ is sliding across a horizontal desk. In sliding $25 \;cm$, its speed decreases to $5.7 \;cm/s$. What was its initial speed if the force of kinetic friction exerted on the pen by the desk is $0.15\; N$ in magnitude? Use conservation of energy.

No. The desk is level so the gravitational PE does not change.

Try again.